I'm sure you'll be fine with the WW Fluid bottle.

Also, in my opinion, you'd have to wait a good long time for enough fuel to evaporate that it would make a difference. I had 3/4 gallon of fuel sitting around for 9 months recently (through the hottest months of the year). When I finally used it again it was perfectly fine.

FWIW, usually transfer my fuel to a plastic bottle, but only beacuse I like to eyeball how much fuel is left so I know if I should bring an extra gallon to the field with me.