Single service butter

Anyone know of a good co-packer for single service butter? We want to include it with our ready to eat popcorn bag. I was thinking the butter may have to be microwaved for a few seconds to allow pouring onto the popcorn. Also, what would be the shelf life of the packaged butter?

For which country?

I think thermoform is best but still you need a cool shelf, you can not stock it in room temperature.