Short of buying a SPARC processor, what emulators are there?
Pickup a second hand Power Mac G5 and you can run a fairly recent version of a mainstream OS (ie. OS X 10.5.8) and a modern development environment (Xcode 3.1.4).
You get a pretty fast, modern RISC machine running an OS that is still highly used (for the time being, I admit.)
You could also install Linux onto it if that would be better for your needs.
Probably a lot easier to find and cheaper than a SPARC machine.