I ended up buying 10 sheets of both V-1 and V-2 Mica via https://www.emsdiasum.com/microscopy/products/preparation/mica.aspx

Measuring a couple of pairs of glasses around our house it seems most lenses are around 5x4-5x5mm. Assuming there is no waste this means that about 45 (WHOA!) pairs could be made.... But lets not get too excited, I'll wait until I actually get the mica.

The total price of the order was around $29.

Thankfully the supplier is close by, so should be here soon.