I've contemplated those, especially the time I got to the first rest stop and discovered that I'd left my baggy off stuff on the kitchen table - ended up perusing a CVS vitamin aisle, those looked the closest but wasn't really sure what 5x or 6x a vitamin C megadose would do. Ended up with gatorade and cliff bars from there, and stopping at a bike shop around mile 31 for nuun.

Ironically pharmacies here in NYC often have bananas (to a depressing degree they can be people's food store, but at least they've realized that and tried to fill the mission); those in the suburbs don't. I really struck out on finding a consumer market potassium source.