Some people offer purchase grit, sand, etc. Some never provide any, just let them find what they need free ranging.
A bag of grit will last a very long time. Are you planning on offering it free choice or mixing with feed.
I just put a small amount in a pvc cap attached to a post and they will get a piece or two when needed. I don't know how many chickens you have, but I've had a 25lb bag for about 3mos. and only used about 1cup, and most of it is still in the holder in the run, at the rate I'm going it will last me well over a year or more.
Not sure of the pricing at your TSC but it's under $9.00 for 25lb at mine.