Dusseldorf

Hi! I arrive in Dusseldorf on June 21 and will be cycling for a couple of weeks, finishing in Paris. I would like to buy a bike in Dusseldorf and sell it once I get to Paris, so if you are selling or know a good place to buy something used, please let me know. Ideally the bike would be not super heavy and around 53 cm, but I'm pretty flexible.

Also, my general plan is to go south along the Rhine, then west along the Moselle into Luxembourg and then cruise into France, but I have no clear plan. If you have any recommendations, please send them my way. Thanks!