You can have a nose around the Ekta catalogue
https://nemigaparts.com/cat_spares/etka/seat/at/893/867850/
Saying that many parts can't be ordered and I think the issue is that the side mounts are missing on the left and right where this has come up in discussion. That's probably another Ekta page and something that cant be ordered unless this is freed up now.
In this page:
https://nemigaparts.com/cat_spares/etka/seat/at/893/867800/
Some people have built their own mods to either lift the boot floor for 4 Drive by 2" or so or put a new one in made of plywood covered in carpet where a double boot wasn't specified, blocks of wood to rest on the sides etc. I think you have been pointed to that one elsewhere.
Basically you are stuck with whatever you ordered for the boot unless you engage in DIY. Spare wheel, that's the Leon one but again the tool kit may not fit nicely away for the 4Drive but fine for the 2Drive. Ekta shows the plastic mouldings that come with a factory fitted spare.