Called around, some auto parts stores have it listed as a Temp sending unit housing or thermostat housing. Nobody has one. Thought I might be able to JB weld it until I can get an ordered one in, nipple broke off when I went to remove the hose.
From searching this forum and others, it seems like a common point of failure for the 3.0 Vulcan.
Word of advice for those searching, if you water pump is wet but it's not coming from the weep hole, it's probably this little sucker. I'll get a better picture of it later, I'm on a hunt. It is stamped with the number 18175.
2000 Mazda B3000 TL Edition 2wd
-Gibson Exhaust- -Gangsta' Tint- -31" A/T's- -2 15" SI Mags- -Sundown SAZ-1500D- -LSD- -Torsion Bars Maxed-
*Eventually: Head Lights, More Tint, 5.0 swap, Murdered, Tube Bumpers, Off Road Lights, Body Lift, Better Stereo, More...