If you verify that your NPSH is actually this low, then you have very few options to pump this stream reliably. Our crude primary pumps have considerably more NPSHa than this and we still have to use vertical turbine pumps in cans to achieve an acceptable NPSH margin for most of our tanks. For one tank, were able to install horizontal, overhung, single-stage pumps with large inducer screws. But, this option would require at least 5 feet or so of NPSHa. Because the flow is so small and the NPSH is so low, I assume you are looking for a heel pump to empty the tank for maintenance. If so, this would normally be done rarely. In our plant, this would be done no more than once per 10 years. I would not install a permanent pump for a service this rare. If you want to drain the tank more often to change crude streams and keep the crudes segregated, then an installed heel pump might be necessary. I would suggest you validate your requirements and then purchase a vertical turbine pump in a can deep enough to give you 10 feet or more NPSHa.
Johnny Pellin