When the kids were little, I discovered that pop bottle carriers make great art caddies. They're inexpensive, light weight, portable, and when it's time to replace them you end up with a great excuse for root beer floats! As you can see our most recent caddy has seen better days, the other side even has a big gash in it. I had tried to use a 4-pack carrier, but it's just too tight to fit all our supplies. Time to replace it.
From experience I've learned that sealing the ends with packaging tape and adding an extra bit of tagboard to firm up the dividers will make the caddy last much longer. Ours usually last about 2 years.
Ahh, freshly organized art supplies!!