Anyone tried the "mylar" collapsable "wine in a box" type bags for storing chemicals? I've been using 1 gallon "canning" jars, with rubber ring, but their wide mouth is not too good for pouring. I thought the bags might be a great solution- not much air contact, light tight (I think), and a handy spigot. I've looked around, however, and I haven't found a good source for these. Anyone know of one?