If you mean the rectangular blocks with the slot and if you are a DIY kinda person, put a piece of rubber in the freezer and it'll cut like plastic till starting to thaw. Put back in the freezer to make the next cuts.
Yep. Pretty cheap at $20 a pair.
Lost mine when I had a 0 mph tip over parking on an incline while fully loaded on a 2 week trip. The fall caused my case to flex in and pop of the rubber block off. It was a mother to get it straighten back.