Mocal oil pumps are about £170, not too bad but i had one, it was soo loud and could be heard over the engine on idle. Plus i read that you can only use the pump once the oil is up to temp, not good for a standalone system. I could be wrong but that would explain why i had problems with it.
Im using a 7 psi pump and silkolene motor cross fork oil. Expensive but been running it for a good month now and its working well. Good flow and temps dont get too hot.
http://www.opieoils.co.uk/p-852-silkolene-05-synthetic-racing-fork-suspension-fluid.aspxI used some compressor oil to start with and it was terrible. Was far too thick.
I then used air tool oil, as it was thin but it was getting very bubbly in the tank so i then switched to the fork oil. I got it for about £20 and its just the right amount luckily.
I looked into spur gear pumps, rather than the (mocal) diaphragm pump but couldn't really find anything fairly cheap.