Foam connect together mats for babies?

We have a spare bedroom that we are turning into a playroom for our 16 month old. I painted the walls nice and would like to buy those ‘square foam blocks’ that connect…they are all different colors. But at Wal Mart they are $20 for only 6 in a pkg…please tell me there is a place I can get them cheaper? Cause we will need about 7 or 8 packages at least.
Thanks in advance!

check on line, or try Target or Marshall’s .