Yup. My choice for 21mm is the non-Asph Elmarit which I had coded by Leica in New Jersey. (Process took four weeks @ $125.00 plus one-way shipping cost.)
I'm still waiting for the 60mm IR-cut filter promised by Leica. Once received, it will permanently reside on my 21mm. When Leica releases firmware 1.10, I should be good to go. (Always an optimist here!)
I use the Zeiss 25/28 auxiliary finder. I'm told the CV metal 28/38 finder is good too but I've never actually used one. The CV choice also has two advantages over the Zeiss: smaller size and lower cost. However, once you put the Zeiss viewfinder to your eye, there's no turning back despite it lofty price.
-g