Something very roughly similar happened to a mate of mine with a sandblasted Harry Boden D2 Bowie recently.
This was my solution, which may be adaptable to your circumstances:
1. Take one baked bean can (remove beans first

) wash the inside out and then dry the can.
2. Using files or similar you need to make a slot in the bottom end of the can that your knife can easily pass through without causing more scratching.
3. Mask off the front of the handle material with a couple of layers of tape
4. Place knife in can with blade protruding from the end through the slot you made, and use any suitable padding and more tape to fix it in place
At this point my mate handed the whole shooting match to another of our friends who happened to have a sand/bead blasting cabinet for small engineering.
He gave the whole blade a quick going over which doesn’t completely get rid of the scratches unless he really went to town, but it does reduce and ‘blend’ them to the point where they aren’t at all obvioius.
The tape and can simply acts as a barrier to protect the handle from the crap that gets thrown around in the blasting cabinet.
I know, I need to get out more...
Worked though, which is what counts.
To make the engraving stand out a little you could use an ultra-fine CD marker to fill the lettering in. If your eyes are anything like mine a jewellers loupe or magnifying glass may come in handy...