Okay, lets try it this way ...
As far as 10mm mags go, check Brownell's. They sell 9-rd CMCs, 9- & 8-rd Metalforms, and they used to sell the 8-rd factory Colts. But they may be out now.
As far as the factory "recoil system" for the DE, more than a few knowledgable people have labelled it "goofy" and prone to breakage (at least that little plastic thingy).
The consensus seems to be:
1) install a steel FLGR in place of the plastic;
2) replace the double recoil springs (which offered an alleged but doubtful 23lbs of resistance) with a single spring from Wolff's.
Here's where opinion is divided:
Some advocate a 20 or 22lb variable recoil spring.
Others recommend a standard spring ranging from 22-26lbs, depending on what types of 10mm loads you'll be shooting.
When in doubt, I personally tend to favor a stronger spring, BUT I would agree that 26lbs is
WAY oversprung unless you're shooting exclusively nuclear level handloads with the 200 & 220gn bullets.
For the hot but-less-than-nuclear loads (i.e., original strength 10mm), I'd go with a 24lb spring and a buff.
For most medium 10mm loads, or especially the milder .40Swishy-Walker level stuff, 20-22lb is sufficient, even w/o a buff.
As always, YMMV. Many happy DE owners frequent this board, so I'm sure you'll receive a range of suggestions.
HTH.