Odds are that you have something old, now unused that you can get the wire from, whether it is solid core bell wire or ethernet cable, multi-strand extension cord or appliance wire, enamelled copper windings off an old transformer, etc.
I mean if you so seldom use wire that you have to buy some for a single jumper, I would see what I could cannibalize, but of course you must consider the minimums of current and acceptable losses as already mentioned, but it won't hurt (if you have space and a mechanical means of fixing it in place) to use a bit small gauge (larger diameter) wire than necessary. This is very commonly done when the design isn't budget constrained down to the last pennies or in your case, saves many pennies if you already have some wire that would work.
