HELP! Lost O-ring on P-Rod.

I lost the O-Ring that goes between the barrel shroud and the end cap.. I believe it is part #13 on the Marauder Pistol exploded view parts diagram.

It is part numbe - 130-035 / O-Ring, Seal .630 .424 .103

I don't know what those last numbers mran, I assume its outer diameter,inner diameter, and thickness..

Is this right and can I find this O-Ring at a auto or hard wear store?

Any help is greatly appreciated.