You have several options when buying pretzel burger buns.  Try your local bakery.  If you don’t see any then ask.  They might have insight on if they will make some or where to get them.  Try your local grocery store.  Check the bread isle, infront of the deli counter or in their bakery department (if they have one).  Even Check the freezer section.  If all those options fail, try your bulk foods store or restaurant stores.   We have a GFS (Gordon Food Service) store that is great for restaurant foods that is available to the public.  If all else fails, ask a local restaurant if they will sell you just the buns.