Tbh that grip looks perfectly serviceable. In your position I'd give them a good scrub with a toothbrush and some warm soapy water before writing them off. Once clean and dry, rubbing a sparing amount of boiled linseed oil into them (and making sure no excess is left as it'll dry to a sticky mess) will bring back some life to the finish.
If you do replace them I'd strongly suggest you go with something that looks period correct (or at least visually unobtrusive) rather than some modern ones in a totally inappropriate colour
