Thx @Flo_Evans for the tutorial on how to do this; I just did it!
A few notes for anyone who's going to try it:
- You don't need to take the big hose off the servo -- that entire assembly will go away, so you can keep it connected.
- To access the place where you put the vacuum cap on, you'll have to take off the left-side panel.
- The MSR bottle I used is 30 oz (about one liter). One of the clamps isn't quite big enough for it (the other one fits fine). So I'll have to get a larger bolt for one clamp.
That's it, good luck! Here's an "after" pic: