A wheeled cart like this is very handy for field BP... and you don't have to worry about Wal-Mart complaining about the stolen shopping cart
http://www.trigonsports.com/Pr...24&category=1674
If the $200 is too much, maybe you can have one of the kids in shop class take it on as a project.
In the cages, we just stack buckets with lids, as opposed to flipping upside down so you don't have to dump everything out every time. We use the buckets with wiffles as the base buckets and/or sit buckets - lightweight and easy to carry around.