They're all over the place. Best price is Lehman's for $3.99:
https://www.lehmans.com/p-1108-mini-....aspx?show=all
2 for $13.50 on Amazon; 12 for $55 on ebay (resell them for $10 each!) and prices all over the place! My kids remember the sprinkling and clothes in the fridge!! I did it all the time! Fun!