Well if you have a fender style bass or a bass that'll take one: Warmoth, Allparts, USACG, and Musikraft are all very reputable and have great marks. I lean towards allparts because of their robust shapes and fit & finish. Warmth has great options that are a bit more custom.
Many luthiers will make parts, Drake Custom Guitars has an amazing reputation and has made some great things for a friend of mine, but worth looking into someone local. Only caveat is that it is expensive and might not be totally worth the investment, but if you know what you want, go for it.
Good luck!