Phil-S

As a follow-up to my earlier comment the wheel I got from eBay from an A3 8V does indeed fit my 2022 A3 8Y. 
 
The wheel you need should have a fitting of 3.5 Jx16 ET25.5 (May look like 31/2…….) which should be stamped on the steel rim somewhere. It has a tyre size 125/70 R16. Don’t always believe what the sellers say it came off or what eBay thinks will fit your car! I think this space saver fits a lot of VAG cars but they charge more if they say it fits an A3 when it came from a Golf! 
I already had a pack of tools (brace, cap remover, towing eye, torx and screwdriver rods etc) but found the full Audi pack on eBay too apparently from a 2021 A3. It’s L shaped styrofoam and sits in the near left corner round the space-saver as you look into the boot. It included all the other tools I had but critically a Jack which was niftilly sandwiched between the styrofoam.
Good luck!