I've seen some Zimbal bags and they have some nice features and are well made. However, their stuff is a complete rip off of Carradice and Brooks and is actually more expensive. So go with the original and buy a Brooks and hang a Carradice on it.
Haha yeah I wouldn't buy a saddle from Zim, but their leather saddle bag has slightly more volume than the Brooks Challenger. The next size up in the Brooks lineup is the Glenbrook, and I have only found that in black, and for 100+.