In your previous post, you mentioned that you would be taking this trip with three others. So is the plan that each person carry their own food? If so, and if the canister is packed efficiently, the Garcia 812 that you rent at the park is going to give you about 5-6 man-days of storage, so one per person will theoretically work. But, you also have to consider that all toiletries, scented items, garbage have to fit into that can at night and/or if the pack is left unattended, which is defined as any time it's outside of arm's reach. For practical planning purposes of canister size and what fits in it, the first day's food, up to and including dinner, can be carried outside the can, but again, whatever's leftover, including trash, has to fit in the can that night or if it's ever going to be unattended at all. It's really not negotiable from the standpoint of either regulations, or if you want a pack that remains in one piece. One way or another, you get caught out with improper food storage, you pay a steep price. One other consideration is a safety margin: A person that goes out for any length of time and doesn't carry at least one extra day of food for emergency purposes isn't looking out for their best interests too well. People also have a tendency to either over anticipate their nutritional needs and pack way too much, or they don't realize that they're going to burn thousands of calories per day and tend to underestimate how much they need. I can tell you though, from lots of experience, my own tendency is to slightly over pack, because I'll take the slight increase in weight over trying to climb a mountain without enough food energy to get myself up, much less what I have to carry...something to think about.
Basics aside, if it's something you intend to use again and want to buy a can, you can get by with something from Bear Vault. The BV450 is slightly too small for five days for most people, so you would need to go up to a BV500 for just yourself, unless you really are good at packing and don't need much food. There are also numerous other manufacturers, and everyone has their favorite. As far as renting a can goes, you can see what a company called Wild Ideas
http://www.wild-ideas.net/ has available. Their Weekender model will hold about 6 man-days of food, and if you decide to share your combined food load (which is going to make meal prep and fuel use more efficient), they also have the Expedition model which will store enough for two people for about six days each (12 man-days total). And of course, you can also buy the same Garcia 812 that you can rent for about $70.