I'm assuming you're talking something like this:
Ateco 826 1/2" open star tip
Use the chart you'll see there to just search by tip number. That site is an offshoot of
CooksDream if you want to also order non-Ateco stuff to maximize your shipping dollar.
Bridge Kitchenware also carries the large tips by Ateco along with gobs and gobs of kitchen supplies. I love them.
I've looked at the Wilton site and it's just too hard to tell from their drawings what they consider and open star tip. Looks more like they're talking about a French star because they have way too many points in their drawings.
Good luck!