Your local medical suppier (supplies Dr's offices, therapists,
hospitals, etc) will have them. Not all of these suppliers sell
products to individuals. Your local well stocked drug store may have
them on the shelf, ... not sure. Check the prices a therapist would
sell them to you for. Anything tagged "medical" will be expensive.
I've used auto inner tube strips (cut myself), also. These leave
blacken marks on your wood a little, but not too much. Wash with soap
and water before first use, after that, no need to wash them. Try them
to see what I mean about blackening your wood. Over a time of about 2
yrs, inner tubing dry rots. Glue is rarely a problem, but avoid glue
sticking to any rubberized strips by shielding your glued areas with
newsprint or paper towels.