This is an old topic but finally was able to get to Harbor Freight and bought "45mm replacement blades" for my Fiskar Rotary cutter. They are sold as "replacement carpet cutter blades" # 97642, $1.49 for a pkg of 2. I was to cheap to pay the shipping and knew I would be going to Spokane so waited. Actually sent my husband in and he bought 4 pkgs.
Not sure who first mentioned these but THANK YOU and to all the newbies, this is a GREAT buy.