Not many high-polish autoloaders out there; maybe a few 1911-style guns that had the flat sides of the slide polished.
Ruger made a stainless-steel version of the Vaquero single-action revolver that had a high-polish finish; looked pretty close to a polished nickel finish to me.
Click link to see one at Ruger's website: http://www.ruger.com/products/vaquer...ss/models.html
I've also seen a few home-workshop-polished SS guns. Some looked pretty good; others, not so much.
I don't know if the alloys commonly used in gunmaking are suitable or unsuitable for a high-polish finish or not, but if the Ruger referenced above is any indication, it may just be market forces at work, not technical problems (not enough folks would buy one, so no company offers them). Gun manufacturers are pretty good at knowing their market.
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)