I'll buy your unfinished inventions

Flexible; to be agreed, Germany

Half-built prototype? Clever mechanism stranded in a drawer? Looking for unfinished inventions with an interesting core. Share photos, what works, what's missing, and your asking price. Especially interested in clever desk tools, small mechanical devices, educational kits, and practical household prototypes. A useful submission includes a short video, a parts list, design files if available, and the single biggest unresolved problem. Ownership of the design and any patent restrictions must be clear before a transfer.