The only Shield EZs with stainless-colored slides are
four distributor exclusive models. Bill Hicks & Co. offers two models with silver matte cerakoted slides and Lipsey's offers two models with satin aluminum cerakoted slides. You probably could not buy the slides separately.
If you just want the slide to have a stainless color, you could probably find someone locally to cerakote or otherwise paint the slide. You could also have the slide plated in nickel or hard chrome.
Mahovsky and
Ford have good reputations for metal plating.