Try W.T. Kelley. I got a package from them and the queen had a problem, so they overnighted me a replacement at no charge. You should be able to get a queen from them overnighted. If their numbers are critically low, you can trade places with a stronger hive. It will fool a lot of the returning field bees into taking up residence in the weak one.
If you combine, put a couple sheets of newspaper on top of a queenright hive and put the queenless one on top. Put the bottom board on top for a top entrance. Make sure it is secured or the wind might blow it off. After a week or so, they should eat through the paper and begin to intermingle with their new neighbors gradually, so war doesn't break out. After they have eaten away a good bit of the newspaper, you can pull the rest off and put the regular top back on. If SHB's are a problem in your area, I would remove any frames of empty comb to reduce the area they have to patrol and replace them gradually as they build back up. Be sure to watch and replace the frames and put on supers before they get crowded to avoid swarming. Good luck!