>>2171562Nautik Argo, about 3200€ with all the kit. An aluminium skeleton, then rubber skin with two inflateable chambers to prevent sinking. Pricey, but fun. It's even sea worthy along coasts.
Best part is to just hop on a train to Cologne, crack open your backpack, build the boat and then use the Rhine to gently drift home. What make/model is yours?
Pic is a random kid i let test the boat. He seemed to have fun.