The Interlight link turned up empty, as the company does not have the lamps and has not for a while. This doesn't seem unusual for some internet companies not to update their sites regularly, at least in my experience.
I have ended up frosting clear 1176 lamps with the Armour Etch that Barkingdogg recommened and have found it works quite well. The cream needs to be left on for much longer than the bottle suggests, but leaving it on for several minutes doesn't seem to affect the result badly. I did tape the metal part of the lamp to protect it from the acid, and then washed the cream off and dried the glass. The only real difference I can tell for the inside-frosted originals is the rough texture. The look of both lamps lit is almost indistinguishable.