hydraulic filter

Hi Cas, I hope you can help me with this inquiry. I have an Ingersoll-Rand air compressor, model VHP750WCAT, YOM 1996. When I bought this compressor I noticed that its hydraulic filters were the LF type (wrong type). I checked at all local filter suppliers (like Fleetguard, Donaldson, ...) for the right HF filter that suits my compressor but couldn't get any satisfactory answer. They all (suppliers) blamed it on the very old model of the compressor which does no more appear in their systems. I just need the reference number of the right hydraulic filter to be able to cross-reference it with available filter brands. Thanks for your help. Regards, Roy