To cover my handsaw blades, I've been using vinyl undersill - it's for
vinyl siding when you cut the top nailer off & need to finish it off &
stiffen it. It comes in 10' sections & I used to just pick up an extra
scrap off a job. I actually had to go out & buy a piece for $3 or so a
few years back. Still have enough for a couple of saws left.
Not all of it is made exactly the same. Look around a little & try to
get the tighter version, if you can. Some is a little boxy & doesn't
grip the blade quite as well.