Did this on my two Matrixes using whatever battery holder was available - with the second Matrix, I was lucky enough to find a CR2032 battery holder that was an exact fit: two terminals with approx. 20.5mm spacing. (And I did make a total ass of myself trying to retain the memory -
you can read about it here
.)
If you can't score a battery holder with the exact specs: It is quite easy to drill a hole for the ground terminal; I did that with my first M1000 and a Renata holder.
BTW: I am a proficient solderer but I positively hate soldering batteries - it is quite easy to damage them while soldering. Daniel has a point though - changing batteries is a rather rare event, the 25-year old batteries from my Matrixes still had quite some life in them. God, what kind of super cells did they use in those days