For this on-line build I'll be using Extratech's “Extrapack” version of the M-10, in 1/72 scale. It contains pretty much everything you need to build an M-10 with the earliy style turret and counterweights. I got the kit from http://www.rollmodels.com/ for $18.50. It’s a little pricey for a 1/72 scale kit, but comes with a nice set of photo-etched brass, turned brass gun, and lots of resin stowage.
In addition to the nice little 1/72 scale plastic kit, the profipack version throws in all these extra goodies.