That looks like a Cummins engine and yeah, those injection pumps can weep pretty bad once the seals start going. The good news is you can get complete pumps for these. Check with a Cummins dealer directly rather than the usual equipment sites. They'll have better stock on standalone pumps and can cross reference by your engine serial number. Also worth asking if it's actually the pump sealing surface or just a connection fitting that's leaking. Sometimes you get lucky and it's just a banjo bolt or line that needs tightening back down. Bolt in is straightforward once you have the right one.