Given an airsource 2250...

 

iso if I'm correct you need part 750-013 it would be urethane in material and you should be able to get them from Crosman

on the adapters I would say yes to the one's by Walther or Umarex

or make you own singles with the adapter from Ebay

I made some at the same length as a 88grain tank for my Hammerli 850's with aluminum tubing and epoxy

if you dump a 88gr tank it will pi$$ you off

I would see if that 013 isn't really the size of the oring

https://www.theoringstore.com/store/index.php?main_page=product_info&cPath=367_1321_1323&products_id=27487