Some S. polymorpha variants from the USA get fairly large and, since they're not so far removed from tropical rainforest habitats, tend to be a bit more hardy. They're also not as dangerous in a toxin sense.
For the biggest and most impressive NA pede, you'd probably want S. heros castaneiceps, which occurs in the Southwestern US and various other areas such as Texas. There are a couple of cool color morphs, as a quick google search will reveal.
There's also a Texas Tiger, possibly another polymorpha variation... These tend to be orange-tan with slightly lighter legs and red head. These we have in stock (with S. heros coming soon):