Suze,
Could you be referring to a "Backpack" ?
They make ALL kids of these which have multiple compartments.
Here's a link...
Ruff Wear Dog Packs
I don't work for these guys, just had it available,
and there are a lot of Mfgr of this type article.
Though I'm not sure if the above Mfg has a Pack exactly like you need
but I have seen them...somewhere. sorry
Have a good Day !
S.W.