For D2 5U13237-up, I have:
9F4111 - Piston assembly which includes 5F0331 ring group which contains:
> 4F6554 - 1
> 8F2154 - 2
> 4F2425 - 1
There's also 5H7269 Piston and Liner replacement group which includes piston as above, liner, gasket, and seal (3 of).
You'll need to determine if your engine fits in that range above (Form 32373 references up through 5U18440)
You'll need to contact your dealer to determine price / availability, and for any items NLA, search on machinerytrader.com
Contact florin, they have them or can order them!
Good source to deal with.
Thanks Nielske