I'm sure there are plenty of products out there, esp for bulk fuel storage (5, 10, 50 gallons). I've used Sta-bil before which came in either little plastic bulbs, like ketchup packets, or in jugs with a mixing device/measuring bowl on the jug, kind of like some 2 cycle oils come in.
For it to work, you have to drain your carb or bleed your fuel line, or run the engine, until the mixed Stabil fuel gets to the carb and engine. Then its supposed to protect the fuel lines and carb from getting gummed up.
Sta-Bil fogging oil (for seasonal storage, spray in the spark hole or intake)
Sta-bil measuring bottle, fuel stabilizer anti-varnish
$10-15 for big bottle (do your gas cans, mowers, cars, bikes, etc)