I'm cleaning up and old Gitane Grand Sport beater to make it a clean beater
Repainted it in the same color, ordered stickers (more expensive than the whole bike was worth when i got it!), cleaned up rust electrolytically, replacing some parts on budget, gonna put on it a Brooks B67 honey color saddle and white perforated Deda bar tape for now

So i need to replace a Simplex rear derailleur for an all metallic one, no black plastic, and not requiring any modification/fabrication work.
Which derailleur should i get? Are there any moderns ones that fit?