you might find a firm bucking at APD (bell and 28th st i believe). if not there, any online store should carry them. like redwolfairsoft.com, airsoftgi.com, airsoftatlanta.com and any of the stores that have ads on this forum.
the bucking does not affect air seal. it acts as a chamber for the bb and hop-up so its open at both ends. that can be fixed with cylinder heads, piston heads, and the actual "air seal" part. again these can be found online easiest... theres not alot as far as physical stores go. :-/