A dual gate mosfet? Or is it so old it only has one gate? I can't
remember.
To a large extent, it seems like small-signal RF mosfets have faded
out. They were big at one time, but then people learned more about
transistors and realized some of the problem with bipolars were they
weren't being used properly. Once they got over the mentality that
the key to transistors were low power, it seems like bipolars got
better at handling strong signals, and the need for mosfets (that
were once touted as being so great for strong signal handling) faded.
So basically you are looking for an RF dual gate mosfet, and one
that won't cost a lot. It's like small signal germanium diodes
at this point, the key being germanium rather than part number.
One place that has a small selection of mosfets, and is set
up for dealing with hobbyists, is "Dan's Small Parts", and
you might look over his webpage at
http://www.danssmallpartsandkits.net
at the very least, it might give you an idea of what might
be available to search for those numbers at some other parts
place.
Michael