I have 3 ParkerHale cocking piece sights for Mauser, click windage @ elevation, fold down like the Lyman but much superior mechanically. Don't know how they attach. Very pricey, if you are interested send me a PM.
gduffy,someone is making Rigbys, I think in Germany, there was a thread here a month or so back with pictures if my memory serves me right. Might be Johanson.