These pattern blocks are so much fun! We borrowed ours but you can buy them online or at a teacher store. Since I borrowed mine, I needed some free, printable pattern block mats/designs and I found them HERE at prekinders.com.
At first, B wasn't interested in the mats and just wanted to make his own designs like snowmen and houses (I mean he made snowmen for MONTHS!). We also use them for sorting and for making patterns.
When I got these out again the other day, B started using the mats and loved them so I went back and printed more. This resource is also neat because they offer the patterns in black and white or in color (which helps children by also giving the color of block that is needed).