I recently polled the CR list to ascertain interest in a machined adaptor to run currently available chain rings on a TA Pro 5 Vis crank.
I've only received a total of 3 requests, so I won't be doing anything at this time. A few years down the road, if TA rings are going for silly prices on eBay, I'll look into this again.
However, I did talk to Roger Durham of Bullseye. He says he has a few adaptors left, that they should do what is needed and that he wants $25 each for them. I don't have his new address, but he can be reached at 1-800-874-0600.
Mark Stonich;
Minneapolis Minnesota
http://mnhpva.org
http://bikesmithdesign.com