One product is indeed called desiccant, it's the polymer-bound adsorbent beads you find in screw on canisters for the end of spray guns,
or in canisters. They can also be called air dryers, water seperators, inline air filters but most call them air filters

Real question Rod is how much you want to spend? Air Dryers can run thousands of $$$$$ and a whirlwind filter can be as cheap as $6.00
-Rebel