They aren't officially for sale due to complex legal reasons (it costs a lot of complex legal money to get them approved as sale products) but you can contact him on the RW101 forums and see if he's willing to make a prototype for you, given proper monetary compensation of course For alternatives you're generally looking at either a pair of single channel controllers (hacked brushless, hacked servo boards, or the Fingertechs for which postage is ridiculous - and I say that being presently only one province away from them...) or something programmable like the Pololu Baby-O which a few people have used.

I've used the Waller controllers in virtually all my antweights (I do have an old dual channel SOZBOTS board which is good, if a bit heavy, but they've stopped making those) and never had a problem with them, and naturally as Peter's at all the ant events customer service is absolutely excellent!