I will be opening the online shop for sales of the Retro Adapter soon (just waiting for the final parts to come in). Both finished adapters and kits will be available, as well as a selection of connectors.
It occurred to me that I can use the same PCB for a Wii/Gamecube version, so I am now working on the Retro Adapter Wii. It will support all the same controllers as the Retro Adapter, and will in fact use the same code where possible. One thing I’m not sure about is firmware updates, I need to look into the options.