Peugeot Performance

Retrobike have copies of a lot of the older Campagnolo parts catalogues which you can use to double check the parts.

eBay is probably the best option. The older 9 speed rear derailleurs should also be compatible as they have the same ratio up till year 2000. You could either replace the whole derailleur or buy a cheap one to cannibalise for the part.

It's easy to identify the older 9 speed ones as they have the b-screw on the mounting sleeve, while the newer ones have it under the guide pulley on the hanger.

"Stupid" questions are generally the most useful questions.

On the basis of what I've read in forums you should be o.k mixing 8spd Campag' components. It might be worth asking Hiarly Stone.

Agree with previous poster about a complete derailleur.

Ebay is your friend here, any 8 speed Campag will work (if it's a short cage that's on there then either short or long cage will fit, the latter with a longer chain, but if its already sporting a long cage then best swap like for like), there's a few on there, or if you just want to cannibalise the broken bit off it, any campag of mid to late 90s (and maybe a little earlier/later) should be close enough.

Campag stuff,  not being as ubiquitous as Shimano commands a bit of a premium - this could turn out to be quite an expensive project for a bike that's not quite old enough to be considered a classic (yet)!

Check out this lot for advice, friendly and helpful

As to the rear mech - It'll probably be rather easier to track down a compleate item rather than the broken part (& possibly not much more expensive?)

As a starting place you could try:

http://www.hilarystone.com/gearscampagnolorear.html

Decals ~ May help V2:

https://www.bicyclestickers.co.uk/collections/peugeot/products/00383-peugeot

Declas - May help:

https://h-lloyd-cycles.myshopify.com/pages/search-results-page?q=peugeot

Try retrobike.co.uk