CAT 302.5C OEM Replacement Oil Pump Needed!!!

I have a CAT 302.5C Mini Excavator. I don't know the year of make, but i know it runs on a Mitsubishi S3L2 Model engine. Currently my technician has opened up the engine because of some engine problems only to find out that the Oil Pump is very bad. Since then i have been on the lookout for a replacement Oil Pump that will match the one that is bad. I will prefer a cheaper OEM replacement because the original is cost prohibitive and this is an old engine that i bought second hand some years back. Anybody with knowledge where i can get a replacement for the Oil Pump? Thanks, Mayowa