Usually standard fit you can go one size up or one size down. But doesn't always work well. Canopy size 150 made by X can be packed a little bigger then same size made by Y. Or both made by X but different model.
You can buy from Chutingstar.
SkySystems Factory Diver Replacement Lens
https://www.chutingstar.com/skydive/helmets/helmet-visors/skysystems-factory-diver-replacement-lens