Most parts houses (Autozone, Checker, Advance, etc.) have them available through companies like TRW, Moog, McQuay-Norris (of no relation to Chuck Norris), etc. ... and I *think* that Energy
Suspension has them available in poly, as well, although I think they're probably part of a total-chassis bushing kit.
But then, considering the work that goes into unhooking the things, knocking (or burning) out the old bushings, pressing in the new ones, and so on ... why not just spend the bucks on a set of aftermarket performance upper and
lower control arms and gain not only new bushings but better traction out of the deal? Do it once, do it right, and be done.
Last I checked, lower control arm bushings were something stupid like $40 apiece, depending on if you have round or oval bushings, and the uppers were similarly pricey ... just for OEM rubber CRAP that will flex and slop around under a load. Yayyyy, wheel hop!
So, considering you can score a decent set of upper/lower CA's for under or around $300 and (theoretically) never have to fiddle with 'em again, the extra cost is worth it, IMO.