Sure, that's a good idea.
Open the lid and determine the mechanism type, then advertise it for sale.

We know for sure that it is used in Japanese Alpine DVD nav units as fitted to many BMWs in Japan.

We also know for sure that it is NOT compatible with the VDO/Siemens/Philips Mk3/Mk4 nav units, which use a completely different DVD mechanism

Not sure how big your market might be, but try....

Got to be honest, I still think your best bet is to go back to the original seller and confront him / try to get the cash back via ebay and Paypal. You've got nothing to lose. Other than sell to Japan I don't think there are any other options. I'd told the original ebay seller that he was selling a unit that wouldn't work in this country yet he relisted the unit and his ad said it was compatible with a bunch of BMWs including E39s but added that buyers 'should check compatability for themselves' - a cop out and I think dishonest given that he had all the facts and knew the truth. Hopefully ebay / Paypal would see it your way - I can even give you the e-mails I'd sent him if it helps...