karma, build your own divider. Get some 3mm acrylic (1/8") from a local plastic supplier, just phone them up an ask if they have any cut-off pieces, you can get them for real cheap.
All the tools you need are a jig-saw and a 3/16" drill bit. I am currently making 5 dividers for my long 17 gallon tank that will hold 6 adult bettas when I am done.