Yes -- The one I bought from Grainger and the one from Chris' are both "Watts P50", both identical plastic bodies. The P50 comes in a bunch of different "sub-models", which vary the outlet size, outlet quantity, and pressure range. The one Grainger carries (or at least the one they had when I purchased) has one inlet, one outlet, and 0-50psi range.
If I hadn't been in a hurry, I would have looked further and tried to find something with a brass body. The only reason I had to replace my original regulator was that I got a bit too aggressive screwing in the gauge and cracked the plastic body.
One of these would probably work:
Or this one, which has a built-in gauge; but I couldn't find it in 3/8" (Grainger only has it in 1/4" and 3/4"):