You can get sheet polarizers from American Polarizers
BTW do not use circular polarizers on e-mount cameras.
It will work, but linear polarizers are more effective and
there is no reason to use a circular polarizer. Those are
for SLRs ... even on SLRs only for convenience, not for
any reason of necessity.
This will solve your reflection problem, but you will still
have the problem of uneven illumination, which generally
requires a symmetrical 2-light arrangement. It's not very
difficult technically, but is a royal pain ergonomically for
You need a tripod or some sort of special purpose stand.
Image stabilization will not help cuz a handheld camera
is drifting toward and away from the subject, which ruins
For the task at hand, there is no convenient solution,
just solutions that are less awkward than others.
Notice on the 2nd photo that some minor scratches are
in focus, showing that focus is correct but the original
photo was not 100% sharp to begin with. So beware of
being confused about focus. Some originals look sharp
enuf at-a-glance, but when you try to critically focus on
them, then they fail to look crisp in the MF maginifier.
Of the 3 lenses you own, you can prolly get excellent
results from the 18-105 in the 50 to 100 range if you
stop down to about f/11. The other two are unlikely to
serve well as copy lenses. You'll seldom benefit from a
"true" macro lens in a portable situation. And you have
no real need to heed any knee-jerk recommendations
that your lens should reach 1:1. Do the math. [FYI your
sensor is 17x23mm].
Your lens will photograph 8x10 prints at about a foot
and a half distance. That is about 1:10. For smaller
originals you need to get down to about 1:4. You'll
need something like this [not expensive] :