I have a Marine Magic triple doser. So far its reliable and has many replacement parts. 90 bucks USD.
It however has some cons. You have to do daily dosing, you cant set it to be like every 2 days or 7 days, it uses 4 dosage rates but with timing to dose, so you have to messure how much its dosing to get it to be accurate to your goal. It has the rates in the manual. You can dose each pump 1 to 18 times a day. For someone doing PPS it is absolutely perfect for the price. It also has battery back up but you have to put some rechargeable batteries in it. It only saves the time and dosing record, it wont dose if the power is completely cut.
Also all my pumps have check valves and I also let it drip into the water, having it in the water presents two possibilities, one it can possibly suck water down outside the tank if there is a leak, two it would leach out ferts from what's sitting in the tubing as the water and the fertilizer would try to equalize, youd end up with a strong accidental dose followed by weaker ones.