I was surprised to see that there was no thread on these. I just got the PERFORMANCE TOOL W89729 from rockauto. It appears ,based on videos I've watched, to be what harbor freight sells. I had my homemade one but for need of the hoses from it to engine I bought this new one. It works a bit different and not sure if I really like it. My homemade one was more like the OTC 5609.
I'm thinking of either using the hoses from the new one on my homemade or replacing the right hand gauge of the new one with a gauge that just shows the psi. I'm thinking the one on it now only has a 15 -25 range because at setup it goes to max at 15-20 on the left gauge. That may be too low for tracking source of the leak. Thinking maybe at least a 30-60 would be better.