As an alternative, any box will do. I've purchased wax nuc boxes marketed under the brand name of MDA (the initials of the man that markets them. You can purchase these through Dadant. Other suppliers have copied the design and sell cardboard nuc boxes, some with waxed cardboard, some plain.
As a trap, they are very attractive the bees, and very light weight, an attraction for the beekeeper. They hold five frames.
However, you will need to build small wooden platforms to hold them on a nail. Pictured below are two of my platforms (very simple to make out of scrap lumber.
I have caught swarms to large they would not fit into the MDA swarm box. Then you have a mess getting them home.
As another alternative, I used apple boxes (picked up for nothing at my local supermarket during the fall apple season). I built little rests out of 1x2 lumber so the frames would stay put. These boxes hold seven frames.
But both these boxes do not hold up well in the weather. They quickly warp and begin to come unglued. However, the price is right and they will do for one season.
If you want to read more about making your own swarm boxes, refer to my article in American Bee Journal, Volume 142, Number 3 (2002) pages 174-177.