Benjamin rebuild an old gen2 mrod / need a set of o-rings for huma reg

Hey guys . . . 'tis the season - at least here in the north east U.S.A. Cold, crappy and (still) mostly dark. One of my farm permissions may very well be letting me switch the lights off in his barns to wack starlings. I've got an older model sightmark wraith scope that works pretty good - doesn't record sound but I don't care about recording anything anyways. My old .177 mrod will be perfect for this - the magazines are easy enough to "helen keller" load / unload in the dark by feel ( I've done it before) so it, paired with that scope will be a good combo for this. I've got a huma reg in it and I suspect that the external ring(s) - can't remember if one or two? - are worn and need to be replaced. (The gun has a slow'ish leak. ) I literally haven't touched the gun in months - 6 or more . . . . so I'm thinking tear it down, de-tune it (drop the reg down to 90 or so bar) and get it going 12'ish ft/lbs with 10.3's and I should be in pretty decent shape. I've got 5 mag's - guessing de-tuned I'll get 80 or more shots per fill ( only a 200 bar fill ) . I can buy a couple of more mags assuming my guess on the shot count is right. More mags, fewer trips out of the barn into the car to reload. :)

Oh yeah the question (lol) - anyone know what size o-rings those are? If so - where can I get 'em?

Thanks . . .

-=- jd -=-