Go to classifieds section about 30 post down someone has a case of poppers for sale sounded like a good price.
just got 10 boxs of kent pro trial for 8.78 a box ballistic products inc
"Poppers" or "blanks?" Most folks refer to poppers as primer only, while blanks make a big bang with some powder. The Fiocchi loads are the loudest (IMO) Gundog Supply/Days End the leat expensive and reliable. (I've had duds in other brand name blanks.) Both sources also offer "popper" loads in bulk.
Mack's Prairie Wing has the Kent ProTrial Cartridges for $79.90/case plus $6.00 shipping. You have to call to order by the case.