Also, if you look in the recipes section, some of the icings/buttercreams will say "does not need refrigeration" or "Shelf stable." You may need to validate the claims. Most American BCs that contain no whipped cream or cream cheese tend to be shelf stable like Indydebi's BC and Sugar Shack's BC; tonedna also has a BC.
Of course all of this is assuming that what you're looking for is American BC not a meringue.
One last thing: Google is your friend.
do a search for shelf stable buttercream