Problem solved. After a slight postal delay, the part has been received, is fitted and working.
I also found this item on Amazon which contains the same spring:
https://www.amazon.co.uk/dp/B0CJTF4VRJ
I hope this thread will help someone in the future.
OK, I think I've found the answer:
https://tinyurl.com/e5n7krh2
Gas strut retaining clip on Ebay. I've just ordered a pair and will let you know suitability.
Credit to my son who found this while we were discussing 3D printing.
My son has a 3D printer, and is working with me to find a solution. It's a work in progress at the moment, so I'll post here to let you know how we get on.
Help! I have exactly the same problem as the OP. I was quoted £200+ for actuator, rod and fittings by Audi dealer.
Does anyone know a source for this clip?
Any help much appreciated.