If you just learned (or are just now learning) that Sticker Mule is run by a hardcore Maga guy, and would like an alternative, may I suggest Sticker Ninja? They are a small but mighty Portland local company and their quality is much, much better than Mule anyway. Their glitter stickers are especially great. They have actual humans doing careful prepress work on your design - one of them is a friend of mine and she's a real pro.
Sticker Ninja ★ Custom Stickers and Labels!!
Sticker Ninja is your friendly sticker print shop!! We produces high quality vinyl stickers that are waterproof, UV resistant, and don't fade! Turning your art into stickers since 2011 :)Sticker Ninja