I'll vouch for the work of David D. I bought a pre-made target style forearm that he had then had him make me one of his Get-a-Grip style grips. (that grip is different than the one in the link tommyt gave) I talked to David a couple of times and gave him hand measurements to work from. That grip fits my hand like a glove.
If something more standard is what you want I can also vouch for Ed's TC's I have bought barrels and wood from him in the past.
Bruce