Ka-bar
 

I have my father-in-law's WWII Ka-bar.It is a Navy issue...he was a Sea bee.
It and the scabbard are in decent shape but the leather disks on the handle are badly shrunken....the same with the scabbard. The things just drips with patina but I would like to restore the leather to it's original size. Do you guys know a good oil(?) to soak them in......ya'll seem to know bout anything worth knowing:D

I keep it sharp and it's no wall ornament but I'd like to pass it on to my son in better shape than I got it.

neatsfoot oil?

mink oil is also one to consider

I bet there is a leather forum on the Inca-net and they will have better knowledge

Yep,
Mink oil. Just be careful not to damage the finish/patina...

Ah, the ka-bar...

Used to be my favourite bar in HCMC...

Check out EK knives the new Ka-bar! The ka-bar can be rebuilt with new leather inserts. There are several rebuilders out there but I don't know where.

I second mink oil.

I still have a Ka-bar knife engraved with my rank and dates of service in a frame on my wall. I keep the one I was issued in my Jeep. They are great knives. You can buy a fitted frame reasonably.

Ka-Bar Display Cases

LEATHER KNIFE HANDLE REPAIR DISKS WASHERS WW2 KABAR USN - eBay (item 280565937765 end time Sep-26-10 08:22:38 PDT)
Those are the disks, you should be able to find DIY instructions online.