Check www.midwayusa.com. They have a wide assortment of magazines. I believe that factory mags are either 8 or 9 round. There probably are some other suppliers which will have a 10 round mag.
I think the 9 round for the 39 series will fit and function, but will protrude from the bottom of the pistol by a few millimeters.
Midway lists a 10 round mag made by ProMag for the 908, which may be OK to use as just a range mag., but I would not trust it for any kind of serious social purposes. For the best reliability, it is best to stick with factory mags or ones from a reliable company like Mec-Gar.