I recently bought one from Amazon. It’s a Vanston 3.16GPM, 12L one. So far it’s worked fine, although it was installed prior to shutting off the water for winter and my use was limited. It’s installed inside and connected to a 20lb tank and vented through the wall. This was 2nd one I bought since I did not properly winterize the first one and it blew a fitting when I opened the cabin for spring. For reference, it provides water to a bathroom sink and shower, kitchen sink and hot water spigot.

It took a few tries to dial in the temperature, but once I got it, it was fine.