Kool Classics (koolclassics,com) have a good range of spare parts for classic Eribas. Worth trying them - I find them very helpful.
Retrocaravanstuff.com is also good - some old parts, some remanufactured. French based, but British owner, Darren, is very helpful.
Ebay searches are often effective too: HYMER ERIBA MOTORHOME CARAVAN WARDROBE BROWN MINI PUSH LOCK CATCH gives a similar catch (but not identical). Remember to search Hymer as well as Eriba, also parts are/were often sourced from other companies outside the group.
What age is your Eriba? I've definitely seen some like it for sale somewhere in my searchings...
Simon