I went with this one https://www.amazon.com/dp/B00P8BE6S8/ref=cm_sw_r_other_apa_i_B6J5EbXMEGAMV
Seems to be working just fine! Good luck man!
You can set up this water heater and pump with 1/2" pvc tubing or rubber hosing . It's best for semi portable setup at a camp but can be broken down pretty easily for travel. You can wire it to a plug for inverter or battery pack like this. or wired to alligator clips to connect directly to a deep cell battery.