http://retro.world3.net/retro.html Cheap and cheerful alternative to the ones you find on ebay. Probably quite easy to build for far less but I don't have the knowledge. I've just put an order in for one so I can use my Neo Stick with MAME. I'll let you know how it is when it arrives.
Nice aesthetics but yeah, pricey, especially with adapters. The parts to make a USB controller are cheap (you really only need a £1 MCU and ~5 passives) but the USB code could take many man-hours, unless you modify someone else's open HID controller as I think he did Just realized he was that BBC guy... heh
