I bit the bullet an bought a new P210 target on GB. I haven't received the pistol yet but I'm anticipating the target grips will be too large for my girly hands. If I switch to the standard grips is there a source for flat base plates for the magazines? Will any other mag base plates fit? How about the base plates for German P210 mags?

The mag for the American P210 is Mec-Gar made. Its body just a little longer than the Swiss and German made mags, so it will look a little funny, even if the Swiss or German base fits.

Take a look at Armory Craft low profile base plates they may be close to what you’re looking for.
https://www.armorycraft.com/pr...e/sig-p210a-base-pad
On my 210 Target I went with their grips and some of the low profile base pads.
This pic shows the stock vs lo-pro together.
(ETA)- the low profile is inserted in the gun in the pic and it matches the profile of the grips.

Same set up here, highly recommended!