Beeman Kodiak Breech Seal

[tacotime666]

I bought a Beeman Kodiak off of eBay and the Breech Seal is in rough shape and I'd like to replace it.  I brought it to the plumbing store, but have not been able to find a suitable replacement.

I saw Archer sells these, but they are $20 for 6, and with $18 shipping for something that could ship in an envelope with a postage stamp, it seems exorbitant.

Any ideas on sourcing a new seal?  In the meantime I might try shimming it with dental floss and see if that helps, but it's pretty compressed, so I'd like to find something new if possible.

Thanks!

[Roadworthy]

Is it just an O ring?  I found a perfect fit for my Diana 34 in the plumbing department of the local Lowe's.