Well, if you are still interested in dry-transfer letters and symbols,
here is a company that will custom manufacture sheets for you. No idea how much this would cost, assuming you can provide appropriate camera-ready artwork.
Back in the day (late 1960s) I used to use these transfers to apply lettering for electronics projects, but only used Bishop puppets for PCB layouts, applying them with their crepe tape of various widths to a velum layout sheet. The completed PCB design was then contact printed onto Kodak A-B photo-lithographic film, which after development served as a contact-exposure negative for a pre-sensitized Kepro single-sided, copper-clad, fiberglass PCB. Following development of the exposed photo-resist in trichlorethylene, we etched the exposed copper with heated ferric chloride. After rinsing and drying, we then drilled the component thru-holes using carbide drills. Sometimes we dipped the drilled board in an electroles tin-plating solution to improve solderability, but there was no easy way to apply a gold-over-nickel plating for contact fingers. Also, this was a long, messy process. And it was pretty much unusable for making double-sided PCBs with circuit traces on both sides: registration problems and inability to make plated-thru holes limited us to relatively simple one-off projects.
As
@Bluejets mentioned in his post #2, you can have small boards made in Asia for just a few bux. These would be double-sided PCBs with solder-plated thru-holes for vias and component leads. We didn't do surface-mount components. You do need to provide the art work, but some of these sites feature proprietary board-layout software. Others will accept Gerber files produced by various PCB design software, such as the KiCAD suite first mentioned by
@bertus in his post #7.
My oldest son, while he was an undergraduate student at The Ohio State University in Columbus, OH, used a laser printer to copy PCB layouts onto transparency films. He then transferred the toner to the bare copper-clad PCB using an electric flat-iron. Results were quick and mostly satisfactory, sometimes requiring minor touch-ups with black ink from a technical drawing pen. The biggest disadvantage that I could see was the transferred layout image could only be used once. So, if he needed a lot of identical boards, a lot of work would be required. However, once he had a working prototype, he could then contract with a PCB house to make a few hundred more. These boards were part of some sort of particle detection system used at CERN's European accelerator that The Ohio State University was involved with in the late 1970s or early 1980s. Good practical experience for a student who would later graduate with a BSEE degree.
You may want to try the toner transfer method to see how well it works for you. At one time I owned two HP laser printers and a Canon laser copier. The printers and the copier all used the same black laser toner cartridge, which cost around a hundred bux back then. Because of the high (to me) cost, I later abandoned the laser printers and laser copier for an HP Officejet 6600 All-In-One inkjet printer, copier, and fax machine. That's what I still use today, even though it costs more than a hundred bux to re-ink the printer. The printer is good enough to make transparent films that I could use to expose sensitized copper-clad boards, but it is so much easier (if not quite as quick to turn around) to use a commercial PCB house like
@Bluejets suggested.
Either the laser printer or the copier (if I still owned them) could have been used to make dry transfers because the toner was re-meltable, but I wouldn't recommend doing that today, unless you are simply curious to see how well it works.
Another possibility is a CNC x-y table equipped with an ultraviolet laser diode to expose a pre-sensitized PCB. Not quite as straight-forward as other methods mentioned in this thread, but good for rapid (overnight) turnarounds. I have no idea how you convert a Gerber trace file into a set of x-y position commands and on/off laser diode commands, but I assume someone has already done this and posted (free) results somewhere on the Web. Of course, if you have a more powerful laser diode capable of ablating (vaporizing) a narrow space around copper traces, you can have a finished PCB without the fuss of etching the unused copper off the board. Be careful trying this at home because copper tends to reflect rather than absorb laser radiation. Always use protective eye glasses with lens that will filter and absorb the laser wavelength you are experimenting with. The reflections are called "glints" and can cause serious eye and other tissue damage. Commercial CO2 lasers might also be a solution worth investigating. These are now available relatively inexpensively from Asian distributers. IIRC, one of the moderators here bought a laser cutter a few years ago. Maybe someone will chime in on whether they are useful for making PCBs.
