Screw pumps have also a good lift capacity and low NPSHr however your flow is very low so that reduces the options (although some manufacturers have small screw pumps for dosing applications)
Small laboratory/pharma hose pumps are also a possibility.
And some small magnetic coupling gear...
Will a flexible impeller pump installed on top of tank make sense?
Those are self-priming and reversible.
I am not familiar with them but I think they tend to be cheap (how much I don't know)
It means that the pump maximum capacity should be 10% higher than your maximum capacity required (just as bimr said), so in fact you are oversizing the pump selection.
If the reason behind this is service life or packing worn I don't know. I will be more inclined to think that is because of...
Those brands, as far as I know, are on the top of the European API675 Dosing pumps market; I will only add Bran+Luebbe as another brand equivalent.
Having said this, that design point: 10 m3/h @ 50 bar is really on the top of any of those manufacturers; you will need to contact them in order...
