Not sure where you're located, but here in the US it's simple enough to buy a pair of reading glasses w/ the right magnification for $1 and cut it w/ a Dremel tool. You can either cut it to size or make it a little bigger and glue it on the bezel around the existing eyepiece. Might take a few tries to get it right, but since each pair of glasses gives you 2 tries, $2 should do it.