Hi Marco,
I think the 22.5mm lens from Flashlightlens will work, just because the ARC LS & the MiniMag with a Sandwich both use the same optics. The Sandwich Shoppe has lenses also. The Shoppe usually has Mineral Glass lens for $1.50 but they seem to be out of them. The Shoppe has 22.7mm Domed Mineral Glass lens for $6 & 22.5mm Saphire crystal lens for $20. http://secure3.dnsaction.com/~anlighte/shop/default.php?cPath=26&osCsid=842c1bad93dd08b65472db706a6ffdff
sorry but the 22,5 glass don't fit in the ARC ,it fit the Minimag but do not fit my ARC-LS1, the NX-05 are 20 mm and i 'm looking for a glass of 20 mm. for my ARC's.