I did a quick check on the auction site and saw several Vivitar 283 conversions. There was a professionally done conversion that looked as well-made as a Quantum, and was priced similarly. Then there were a pair of rather amateur-looking conversions selling for about $150 each. They looked a little klugey, and I'd be worried about their durability and safety long-term. But they exist as an option. A final thought - just get a Gary Fong light modifier with a chromed interior. Or take a quart-size plastic takeaway soup container, spray-paint the inside silver, and cut a hole in the bottom for the flash to go through.