Another option is that you can set up the job and mask the wood. Then lightly cut the outline of the saber. Peel it and then paint the inside with a light color (or even glow in the dark). Then engrave as usual.
You’ll end up with a high contrast via paint which should be more durable than the tape.
As I often use WBPU to seal wood, I have just brushed that over masking as well. It’s not a vivid as painting, but as engraved wood is somewhat “antique”-y anyway, it looks just fine.