The lenses sold through the above link aren't an exact match for the original lens pack (red, green, blue, amber), but they're an excelent replacement. They never made a dark blue like the factory blue lens (ie: not the "purple" that came with it).

I wonder if BC Laserworks (aka: Filener) is still selling them. The ordering page is a little tricky; in the middle of the page, select color and quantity, then add to the PayPal cart.