You can ROLL YOUR OWN very cheaply - any size
buy an inexpensive roll of whatever thickness of
clear vinyl you want at a hardware store
make a template (I use 1/32 inch aluminum
Cut 2 pieces slightly larger than the template
and use vise grip & a hot nail or heated icepick
to bond the 2 pieces together (except one end)

I seal all 4 sides and cut one end off neatly
with a razor blade knife to make the opening
I started doing this to make LP covers due to cost
(and often unavailability) of the regular vinyl
covers at the record stores

You can leave some Xtra on one side to punch holes
for a 2 or 3 ring binder