Here is a better closeup of the model that I used - Full scale reading is 2.0 GPM which is just about perfect for our loops.
These models feature 1/2" BSP outside threaded and 1/4" BSP internally threaded ports on the rear so you can just screw in our standard G1/4" fittings directly into the unit.
I purchased mine off eBay direct from China since I'm located down here in Australia. You can also purchase the exact same model at Walmart - I see you are in Texas so not sure if Walmart is a more convenient option for you or not.
Walmart Link