im new to the forms but i actually have been following this topic closely and going back and looking at what every one has posted and i found this
http://www.airbagit.com/Billet-Wheel-Adapters-Adaptors-Spacers-p/aa-4140-4100-ib125.htm
http://www.airbagit.com/Billet-Wheel-Adapters-Adaptors-Spacers-p/aa-4140-5100-4-5ib.htm
they are made from T6061 Aircraft Aluminum
i havent gotten a response from the dealer but hopefully i will soon
also im more of a street guy and i did do the six bolt conversion on my spare hubs worked great (im running 15in rims now they look sweet) but i love the idea of more wheel selection on these sweet cars we've got and just thought i would share