They were made by Boeschebuilt and sold directly from his shop. I do not remember Smart Madness ever having them for sale. They were $150.00 and then a rebate of $55.00 when you returned your stock paddle shifters. I elected to keep my originals.
He also made armrests, and inside rearview mirrors for the smart. As far as I know, he has stopped making any accessories for smart cars.
I have found some Chinese made paddle shifters on E Bay that stick on the backside of the stock smart paddles. They come in a variety of colors, are made of plastic, and are under $30.00 if I remember correctly.