I happened upon a Harbor Freight last week and went in and asked about carpet cutter blades....the woman at the cash register didn't have a clue...she directed me to some electrical gadget that cuts carpets..or something. I knew that my rotary cutter wasn't electric ....so the blades were probably not either.
I found them on my own.
They are : "Replacement Carpet Cutter Blades", Item # 97642. they came 2 to a package for $1.49,plus tax. I haven't opened them yet. Keep in mind they are for the smaller of the rotary cutters..don't know numbers, but I do know they won't fit in my larger cutter.