Is there any way that the sushi could be made in a way so that it wouldn’t be contaminated by gluten?

Don't use Soy Sauce......,👍

Soy sauce would be the main source of gluten for sushi. It would be difficult for a Japanese restaurant to assure the exclusion of soy sauce to anything in the menu. If you are not very sensitively allergic, you can avoid >90% of gluten by not using any soy sauce, on your own risk, of course.

Eat something else then. There's plenty of ways to prepare fish