Boxes for Red's Meadows Store are sent to a P.O. Box at Mammoth Lakes, California. Mail for Mammoth Lakes, California, IIRC, arrives by truck from Southern California once a day; depending on the truck origination point, drive time can be five hours or more. Mail to Mammoth Lakes takes a day longer than to "normal" destinations plus there is sorting time at the Mammoth Lakes Post Office.
A Red's Meadows Store employee picks up at the post office four times a week and takes items to the Red's Meadows Store. Driving time is about 45/55 minutes, but truck might not head directly to Red's Meadows. Package could sit at the Mammoth Lakes Post Office for a few days before pick up by Red's. I would allow at least a week for an express mail package to reach the Red's Meadow store.
Another option is to take the ($7.00?) shuttle bus from Red's Meadows to Mammoth Lakes, where one can buy all resupply items at markets, outfitters, etc. Or, mail a box to yourself for pick up at the Mammoth Post Office. Mammoth Mountaineering sells denatured alcohol in small quantities; bring your container. Mammoth Brewing Company makes a good rehydration beverage, which is sold at most restaurants in Mammoth Lakes.