This was something that just wasn't worth doing for LE, because it was too small to justify taking up an esp slot. Now there are esl's I can finally do it, for SE only.
HF Materials provides recipes for cullet (smash an empty bottle) Glass = 6 cullet, both at the smelter, and you can mill 15 wheat at once to get 5 sacks of flour and one Straw. So now you don't have to deal with merchants at all.
This will probably be the final version, but I'll leave it as WIP, in case anyone finds a bug, or thinks of anything else it should make.