I'll try to help where I can. I have scoured Vegas for decks. The best place to find vintage, uncancelled playing cards are at antique malls nowadays. It's a very rare thing to see, but sometimes you can get something nice. Because of how antique malls are organized, you'll have to spend 1-2 hours investigating every nook and cranny of the booths to find a single deck or less.
Now there are the obvious places to check: Hotel gift shops. Here you will find the newest cancelled decks, and this is the best place to try out the finishes and stocks on Gemaco, Paulson, Cartamundi, etc. Do NOT buy any of the decks that look like they're not cancelled. They're cheap garbage and almost on par with the Cardinal's decks in terms of how terrible they are.
Next stop is Gambler's General and Spinetti's gaming supply. The former is owned by USPCC and has a huge selection of decks. If you're looking to find $100 decks for $5, you're out of luck. If you want to find $10 decks for $3, you're very much IN luck.
Spinetti's isn't owned by USPCC and they have a decent selection as well. Their stock shifts around more often and it's a complete guess for me as to what they have now since I last visited them almost a year ago.
Now let's address your desire to acquire Wynn decks.
You will not find uncancelled Wynn decks anywhere, ever, at all. At least not on a vacation visit.
However, there are cancelled brown, red and violet Wynns ALL OVER Vegas. Yes, they are of the "logo" variety that sell for $15-45 per deck sealed and uncancelled. They can be tricky to find though. I have spotted them in stock by the brick at various playing card booths at malls. You really have to look around to find the decks in the booths, but finding the booth can be tricky as well! There are three booths worth noting that I have always seen the logo Wynn's at: Miracle Mile Shops, The Fashion Show Mall, and the Outlet Mall. There are more than one "card" booths at each of these locations, and I can't help you any further beyond telling you to scour every last inch of the places.