I know exactly what you're saying... I frequently play bass for a local band and if I have fingernails I end up chipping them. Not like breaking the whole nail, but just little chips in the nails which means I have to file them down. Basically, I haven't found anything to protect them. Even clear nail polish doesn't protect from those little nicks. Back when I used to play classical guitar at weddings (before I moved here to Minneapolis), I needed my fingernails; they were important to my income. Now that bass is what I play for money more than classical guitar, I find that I have to just keep my nails short. I like fingerstyle guitar, but hey, I gotta get my bills paid.

My one suggestion to to just be careful when playing the bass. Make sure that the pads of your fingers strike the string adn that you don't drag your finger off of the string (this is where the string bites your nails). Pluck through the string and just pray that it doesn't catch a nail.