I have a rather vague recollection that gold has been transmuted from other elements in experimental (fission, I presume) reactors as well, although the best reference I can find right now is [1]. Accelerators do seem to be the modern/"practical" approach though.

Which properties in particular make it a good target?

Edit: more details from wikipedia[2] suggest starting from either mercury or platinum, although it's all a bit fiddly and isotope-specific. That page has some other interesting facts as well - I'd never really thought of element synthesis as economically practical (and with capital equipment costs, probably still isn't), but tungsten ($30/kg) -> rhenium ($6k/kg) -> osmium ($12k/kg) sounds like a nice business to be in if you can solve the practical problems.

When the balloons all run out, we might want to start making our own helium as well, which has the bonus of being really quite easy to do.

[1] http://chemistry.about.com/cs/generalchemistry/a/aa050601a.h...

[2] https://en.wikipedia.org/wiki/Synthesis_of_precious_metals#G...