It all depends on the articulation you're looking for. I have had success rewrapping old timpani mallets with non-standard wraps. I didn't want to deal with the wool "fluff" anymore, so I used felt strips for one set (enough to wrap around the mallet head 3 times), and also rewrapped one a la marimba mallet style with yarn. The yarn gives a softer articulation, and sounds like T3s, while the felt sounds similar to Goodman greens, although heavier so not quite as articulate.
I have found a decent set of timpani mallets for cheap(er). I do a bunch of musicals, and am always needing to use Vic Firth SD12 (Swizzle Sticks) anyways, so I figured they might work for the occasional timp parts when stick transitions would be difficult. I mostly use just those for musicals now, except for when I need something extremely soft of the timps. They sound surprisingly great!