I found these 8pks of CR2032 at IKEA. At $1.99 for 8, that makes each battery $0.25 each.

There are some places online that you might be able to get these a little bit cheaper. I saw an ebay auction that had a 5pk for $0.99.  So that is $0.20 each but then factor in cost of shipping. So if you have an IKEA nearby and you need some CR2032 for your Red Dots you have a place to get them relatively cheap.