You can get the electrolyte tablets from GNC stores or many of the on-line cycling stores like Nashbar and even Amazon. I wouldn't be surprised if some grocery stores had a few types as the runners like them, also. My LBS has them and I am there regularly, so ou'll hve to decide which options you'd like.

I'm with you on the cold water, too, I fill my bottle with ice to the top, then add water. If I am going to go out in really hot and humid conditions I'll freeze the water in the bottle (don't fill it full, the expansion will grow your contents past the top or bulge the sides, possibly splitting your bottle.) As the water melts I have nice cold water to sip as I ride. No problems here with thawing, either, it is usually in the high 80's to mid 90's during the summer and early fall.

Bill