Old bike for challenge (scrap/broken) (Roche PL26)

I'm looking for an old bike for a very special challenge. Every year we do a memorial weekend for my friend Fran in which we set ourselves a cycling, walking or running challenge. This year marks 5 years since he passed away so I'm looking to do a special challenge for it. My biggest challenge since my injury.

I'm looking for an old bike like the picture. I don't want anything good, in fact I want rubbish. Old Raleigh, Apollo, basically something with thumb shifters and either 15 or 18 speed. I'm aiming to do a 50 mile ride on a bike saved from scrap. I want it to be difficult as that's the longest ride I'll have done since 2019 and I want to really do something special.

Does anyone have anything lying around that might be suitable?

As close to Roche as possible please. Thank you.