I don't know how Zeagle installs the ring but I think it might be RF welded in place. It's not something you could replicate at home even if you could get the ring. You might be able to glue it in place with Aquaseal but it would likely be messy and I am not sure how it would turn out. Furthermore, I don't know if Zeagle sells the ring uninstalled.
Most manufacturers extend lifetime repair service to original owners of BCs but without proof of purchase you are going to be lucky if a dealer is going to take the time to ship it back for evaluation. However, you could ask if Zeagle would repair the BCs if you pay for parts, labor and shipping.
Warranty service is part of what you get when you purchase a product new from a dealer. Whatever brands you look at to replace the Zeagles, I would suggest buying new for peace of mind in the long run.