Adult son thrilled with new trap hobby. Asks about ammo sales..

My son was introduced for the first real time (by me) to trap shooting using his handsome Mossberg 500 with vent rib and a selection of choke tubes. This gun he bought from a long time friend wanting to fund a revolver. For $200,, son received the gun in pristine condition, a box of ammo, a cleaning kit, a soft carry case, the extra factory chokes and as said, the factory vent rib. I threw for him at the club range, and lo, he hit 90% first time out!
Bad part: he used all his ammo. Asked me if I could keep an eye out for 12 gauge 2 3/4 inch 1 ounce 7 1/2 or 8 shot. Said Cabela's has an OK deal (he thinks) for about $5.50 a box.
Anyone aware of any of the big outfits or some of our other haunts besting that price point maybe?
I used to load 12 gauge,, but my old Texan FW back i the early 80's is long gone. I'm not a frequent shotgunner though, and suggested that he's be better off at this point buying his ammo for now.
Thanks friends, and good things hoped for all.
Don.

Say thank you all for the help. We do have a Dunham's locally. I too will check the big boxes like Walmart. The days of $3.50 a box if bought by the case of 10 boxes close to dove season are gone. Last time I got that deal was 6 years ago. Don.

I did tell my son what a great score he posted. I told him that for me, trap was like bowling. Some days I just killed it,, folowed by a stretch of "well what was that??" Loving his interest folks. Don