Thanks ctrysass2012 for comfirming what I suspected!
I just looked up the blades and 2 cost 12.99 on Amazon which also states that the blade works in Olfa, Fiskars & Clover as well. I put them on my wish list. BUT I am seriously thinking of ordering the other Martelli (45) cutter. I don't think I will order extra blades for both since I am more and more convinced that the Martelli blades are much sharper and last longer. I do lots of cutting at once for Project Linus tops and the ergonomic design of the Martelli along with the sharpness really speed cutting along.
I do continue to use the old Olfa cutters. I have a small cutting mat to the left of my machine and when I need just one or two more pieces cut, I grab what's handy (Olfas) and go. The major cutting area is where the Martelli lives.