I bought a Seaflo series 42 off Amazon. It’ll be here tomorrow. It’s selling points to me were a 700 hour motor, runs continuously at low flow levels, 4 diaphragm chambers and emptying the tank won’t harm the unit. It looks identical to the Shurflo 4008.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1