The alloy Delrin Valves are the best. Use a very little marine grease on the rubber gaskets when refitting.
Ron Hale Marine Ltd - Zodiac and Bombard Spares
You need (per valve) diaphragm Z2195, valve cap seal Z2213 and a gasket insert Z3293.
The nickel plated valves you can still get, but apparently you can't get the caps, until I found some on an Australian site. Predominantly found on vintage Zodiacs.
The gasket insert looks more difficult to source as it usually comes as part of the assembly. My memory of that gasket is it's a little deeper than the base gasket Z3001.
Anyway - double check everything before you order.