Dumprat,

For a right-handed shooter, the main advantage of a side swing safety with a left hand lever lies in the convenience of operation by the thumb of the hand that hold the grip.
It's much quicker and easy, as you don’t have to release the grip.
In USA, Satterlee Arms' - http://www.satterleearms.com/index.htm - offers a good left-side three position safety for $350.00 installed on your Mauser
Here, in Europe, we can use the version produced by Recknagel.

DORLEAC
www.dorleac-dorleac.com