There's not current listing for any for sale here.
If you are on Facebook I would suggest checking or posting on the AHRMA Swapmeet Facebook page. Used ones for sale aren't very common.
There are a few AHRMA members that build them.
Buying a new one will cost you $1,000+. I bit the bullet and bought a new gas engine powered one from Land Industries. They're racers with a fabrication business.
Doc Z roller starters are also popular.
Are you coming out to play with AHRMA this year?