I have Stowaways. They make them for English and western saddles and have quite a few options/models. I don't think they'd do for a weeklong ride, though. It seems you'd need packing gear for that?
Here is a nice "large" set of saddle bags, that I would like to get this spring for myself

it looks like some of the compartments are detachable, and there looks to be quite a lot of room!
Hello, I have been using a set of A T V gas tank saddle bags purchased from Wall Mart several yrs ago-were under $20 then, they've held up well, have many compartments, easily accessible as they already have” the hole" and fit over your saddle horn- keeps everything in front of you. Has worked well for me for many yrs of riding. Check me out-good luck.
I have a horn bag that I use for day trips and saddlebags for longer trips. Whatever you end up getting please is careful about one thing. When you pack them, please distribute the weight evenly on both sides. It makes it so much easier on the horse. I find it so annoying when riding behind a rider whose bags is obviously weighty on one side and hanging down.