I haven’t installed it yet... but ordered this one from Amazon.
RioRand™ Upgraded 6V-90V 15A DC Motor Pump Speed Controller https://www.amazon.com/dp/B00F839VNQ/ref=cm_sw_r_cp_api_.uirAbBCYD7YD
The eBay one is cheaper if you need 5, but I like the amazon return policy better if things go wrong.