I tried carrying butter the last trip I went on. I put it in an empty film canister, then in a zip-loc bag. Thankfully the zip-loc worked out!!! It was a mess, but well worth it for the breakfast oatmeal and grits. Maybe a small rubbermaid container or even an empty pill bottle, but I would still keep it in a bag so that you don't find out the hard way that it isn't air-tight.
I also tried that squeeze butter on a weekend outing. It isn't the best butter, and far from the lightest way to transport it. But if they made it in a smaller bottle, then it wouldn't be too bad because it never leaked and it was still good on the trail.
But, there is always going to the local breakfast joint and getting those little bity tubs of contry crock they give - I know hotels give them out with their breakfast, and I've seen them at like IHOP or Denny's. Maybe Sam's club would have them, or a local resteraunt supply store.