showing the same info on multiple posts

Hi there,
I desperately need some help. I’m working on a material database for students. Each material will be one post, let’s use Oak as an example. At the bottom of the post I want to show a list of addresses where you can buy that material.
So for Oak I want to show a number of wood shops. But for another kind of wood I’d like to show the same list. This list will change in time so I’m looking for a solution that i can work in one list, and that it will be corrected automatically in all the posts. I looked at Iframe, fields, ghost images, plugins and widgets, but i can’t find a solution.

It’s probably very simple but i’m stuck for a day now and really appreciate any help, hints, or suggestions! Thank you in advance!