I use a powder-filled puffer bottle to check the wind direction while I'm hunting. It's easy to go through a lot of powder in a short amount of time, and the refills can be very expensive.
Powder substitutes like baking soda and cornstarch either clump easily or are too heavy to hang in the air for long periods of time, so I did some research and found a much better option.
Surprisingly, the best source I've found comes from scuba diving supply stores.
Divers use unscented talcum powder to make it easy to slide their wet/dry suits off and on, so they have to buy in bulk.
You can buy a large bag of talc for next to nothing, and it will be much cheaper than most hunting supply store refills.
One bag should last you several deer seasons, so find a dry place indoors to store your talc in order to prevent clumping or mildew over time.
I hope my tip about buying refill powder in bulk from scuba diving supply stores will save you a ton of money.