Many paint companies offer clear coats that will offer protection. Some will be a gloss-others a matte finish. I've found spray enamels tend to work well. Laquers are available also, as well as other types of coatings. The old disclaimer- try out on a small hidden area first to ensure it doesn't affect the primary finsih. A trip to the hardware or craft store is in order. Have fun!!

I simply use the walmart brand of clear spray. But others like Rustoleum and the more expensive brands.