I'm sure if you scrounge around your local area you'll come across a barrel. But here are a couple of options to hash over: Mixing small amounts at a time that you will use for each job (5 gal. buckets) Another option is go to an agriculture supplier like Tractor Supply and buy a 35 gal. container for your mix. I think they're around $65 dollars, but you'll get a lot of use out of it, they're horizontal and will sit steadily for transport. I bought one ten years ago when I got started and it's still holding up just fine.
Jeff