I have used a large plastic wheeled tool or tote box that you can buy at Home Depot, Lowes etc. I got one with the bigger wheels that makes it a little easier to roll over curbs ruts etc. You can pack a lot into one, although you will need to devise away to secure the camera from moving around. One advantage is it is sturdy enough that you can stand on the top which provides about 18" extra standing hieght if you have to go high with the tripod.
i can fit my Eastman Commercial 8x10, light meter, three lenses, dark cloth, 6-8 film holders, filters, small set of tools, loupe, bottle of dust off, and my 35mm with a couple of lenses. I strap the tripod to the top with some nylon bungee cords.