Tire Equipment Supply and ProQuip seem to be the main two distributors around here, at least the ones that come up on Google.
I would skip the screw on type pin plate unless you're only ever going to drive MB for the rest of your life. Check out the SpeedPlate from MT-RSR. 10% off your first order if you sign up via email.
I'm using that in combination with a Haweka duo-sided low taper collet. To be honest, I should've gone straight for the expanding collet. I am going to pull the trigger on one, just haven't gotten around to it yet.
