I've refurbed alot of older knives where the handle has shrunk. Recently I had a knife with a similar situation. I was able to make a thin black kydex spacer and tap it into place where it fit in the original spacer pattern.
I made it donut shaped, then removed one third so it could slide over the tang. I roughed it up, coated it with epoxy, tapped it into place, then tapped in the remaing 1/3 piece (also coated in epoxy) and wiped it clean. The next day I sanded it down and oiled the leather with neatsfoot oil. It looked as good as new. You couldn't tell where I had spliced the spacer together. It all blended right in and tightened everything up nicely. Hope this helps,
Scott