Where to buy: Amazon
Measurements: 66% maltodextrin and 33% fructose
Salt: Mimic what works for you in other sports drinks
Use a food scale for all of the above and you should be happy.
Note: Maltodextrin mixes best in warm/hot water. I put a little hot water in my bottle, mix it up, then add ice and cold water. This tip works well for Beta Fuel and Maurten too.