At first I thought you meant aero wheels, but you mean disc brakes I presume? if you can't find a ready built wheel just have one built with the disc-brake hub of your choice.
Go to www.trials-forum.co.uk theres a whole load of new 24" trials stuff going on and alot of them use some good street/ jump gear, you can get some real bargains on it.
ill have a word with a few guys round here i used to ride downhill and a bit of street ringing with but i can't promise much mate. have you tried ebay? gumtree ect?