I have four Exo-bins, which work awesome for fermenting beer, wine, cider or other. I bought them before we had a building and no hot water, creating a sanitary system in an otherwise non-sanitary outdoor environment. These Exo-Bins fit about 240 gallons comfortably, which is good for weight. If you found longer pipes (these were modified down by previous owner) you could fit the full 300-gallons.
I now have a hot water and sanitary space but will keep using them in future years for extra storage, however they're a better use for someone in startup mode like me.
Four Exo-Bins - $550 each (Bottom hard plastic, Top hard black plastic, aluminum pipes, white tarp for cleanliness and stability)
About 45 sanitary plastic fermentation bags - $1500 for all (Plastic bladders that fit inside Exo-Bins)
Attachments - $100 - Paper Systems (company that makes bags) sanitary filling and emptying equipment (flat cross-bar, attachment to tri-clamp)
Package for all - $3,200