What CO2 pistols could you actually rebuild?

I have an Umarex that I really like but I'm only seeing the CO2 bulb seal for sale overseas like in the UK I called them and they told me they don't stock them obviously they just want you to buy a new gun. I'm looking at some of the daisies like the 408 so what I'm asking is what co2 pistol could I buy knowing that I can rebuild it if it starts to leak? I'm assuming it would be a Crosman or a daisy but to be honest I'm not having a lot of luck finding those seals either. Let me know what would be a good pistol to purchase that I could rebuild it doesn't matter if it's pellet or BB. Thanks in advance
 
O-rings are fairly easy to get hold of from multiple vendors here and there including eBay. Here is one vendor;

https://www.oringsandmore.com



O-rings are all most guns need. If they need more it's best if they are Crosman as several people have parts for many of the older guns including;



Precision Pellet in Pa;

http://www.airgunshop.net/index.html

[email protected]



Mac1 in CA;

https://www.mac1airgunshop.com/



SW airgun repair and has a limited supply of some parts.

email or call for info;

[email protected]



Grips for airguns;

Steve Corcoran

https://www.scstocksandgrips.com/



22xx stocks;

Tom West

https://urgthrash.wixsite.com/squirrelmaster



Vernon Austin;

[email protected]



The list for aftermarket Crosman parts is extensive;

https://www.airgunnation.com/topic/any-2240-hpa-conversions-out-there/#post-1197392