I got a no-lock 642 recently and just received my MIKA pocket holster earlier this week. Google Bob Mika and you'll find his site. Best investment in a pocket holster is what my friends told me. After getting one in hand, I am very satisfied.
You might want to rethink one thing you posted, that you don't plan to shoot the 642 much. I believe you were referring to the light weight being a joy to carry, but maybe not a joy to shoot all that much. The other side of that coin is that to shoot any snubbie very well, even at bad-breath distance, you need to practice. Dry fire would be good, too. Yes, it will go bang for you. But, you really do need to get the hang of shooting a snubbie.
Here is my favorite site for snubbie information.
http://www.snubnose.info/accessories.htm