We just got the first four books from the library. Our local library district didn't have it but we did a search on the broader system which allows us access to stuff from the whole Front Range (Ft. Collins to Colorado Springs) including everything from municipal libraries to university libraries. We've had good luck tracking down some pretty obscure stuff. Have you tried looking beyond your local library system?
DS loved the Murderous Maths series so someone suggested these. So far, DS has given them barely a passing glance. "Mom, it's SUMMER." Next week his older sisters are away at camp so maybe he'll be bored enough to sit down and take a look. I'll let you know if we have any luck.
