BigDye® v1.1 & v3.1 5X Sequencing Buffer Makeup? - (Feb/16/2007 )

We are now using BigDye® Terminator v3.1 for our sequencing after switching from another service who did it for us. The first time I set up the reaction instead of doing a 1/16 of a reaction (common), I guess I did a 1/32 of a reaction by using 0.25ul of Terminator mix per 10ul of reaction. I got great results with up to 750bp of clean read. I know most people do "diluted" reactions, but the problem now is that I am going to run out of the Buffer before I run out of the Terminator mix. Of course, we could buy extra buffer, but at $50 for 1ml...it seems a little ridiculous. Does anyone know what exactly that sequencing buffer contains? I know it is probably proprietary, but I thought someone might have an idea about how to cook up a little more in the lab.

400ml 1M Tris HCL pH9.0
10ml 1M MgCl
590 mL H2O

better if not the same as 5x seq buffer...