Or, if you really want to keep the original finish intact/unchanged, you could simply put on a couple coats of paste wax-- like SC Johnson paste wax (yellow can, available at Home Depot)-- or other good quality wood/furniture wax, or gunstock wax, or bowling alley wax.
You'd probably need to reapply a coat of wax every month or so, but it's quick and easy, protects the original finish, makes the bow look great, and should provide the finish cracks with a decent level of protection from moisture penetration.