That's what my Cheely grips use. They come with a couple of baseplates that are necessarry to get the STI magazines to flush mount. You can order more as needed.
@Bakerjd I'm sure Mark would be happy to build a Commander for you to carry
Carne sight block commander with a Cheely stainless grip. I'd lose the massive magwell, though Cheely has a tactical magwell now.
Carne Custom. This one is just a little under commander length (4 in).
If you can live without the aluminum grip, the Bul Tactical Carry Commander is very nice. Also. affordable