Drue, If you are going through blades quicker now you may consider a new mat or turning your current mat over if possible. The self healing mats can get stuff stuck in the grooves when you cut and when you run over it that will put a nick in your blade.
I would also call that HF and ask them if they carry carpet blades. They don't have a clue what a rotary blade is because to them that is what they are called. I have yet to go into any HF store and not have carpet blades. The item number is 97642 and that may help them know what your are talking about.