One great brand of flow meters is Zee Line, which offers different types of flow meters in different price range. Check out some of the summaries of the models below and let's see if one of them suits your pump.
This low cost flow meter is suitable for use with oils, lubes and coolants. Made of rugged glass-filled nylon case and aluminum housing on the oscillating piston metering unit, the flow meter dispenses in pints, quarts, liters or US gallons up to 1000 units and totalizes in liters or gallons up to 100,000 units. It has simple two-button operation with 5-digit liquid crystal display with 15/16" high numerals. The flow meter works with a lithium battery power unit that stays for 3 to 5 years.
This Zee Line flow meter comes with 1.5" NPT inlet and outlet and is priced at $291.54 each.
Another electronic flow meter is this Zee Line product with trigger-operated nozzle. Also designed for petroleum products and other automotive liquids, this flow meter has more or less the same features with the electronic flow meter discussed above. But with the lightweight and perfectly balanced nozzle, this flow meter has a comfortable grip when dispensing the petroleum products at the flow rates of ¼ to 4 GPM up to 1500 psi. Priced at $409.20, the quality matches the price as it is tough and provides accurate measurement.
For motor oils, you may want to check out this Zee Line automatic dispenser and flow meter. With an automatic metering, the flow meter performs accurate and waste-free delivery. Constructed of all metal with Buna-N seal, ½" NPT inlet and outlet, the meter is perfect for high volume use. All you need to do is to set the dial to the desired quantity (1-60 units) and squeeze the trigger.