I was at Ross Dress for Less yesterday with my mum and we found some great bags of shells for pretty good prices. Just wanted to let you know in case anyone's looking for them right now. I picked up 4 bags of assorted shells for $3.99 each and another bag of the same kind of shell (don't know what they're called, sorry!) for $2.99. Hope this helps someone!
Here's a pic next to a pint glass so you can see sizing of the bags. I haven't opened them yet, so I don't know how many shells are in them, but they are in very good condition: I can only see one broken one in all five bags without opening them.