The Drunken Lizard Pub

I need to get the charm spell so I can use it on Erubor to make him friendly again or else he'll own me when he sees me again.
But I've been sitting here for 2 days (Real days and not game days!) and I can't find it in any store.

Is there a limitation to a level in which you can buy the spell? Like a diamond claymore. You can't buy it at level 5, but you can at level 12. Something like that. Cause I can't find it and I need it! Or else Erubor is totally going to OWN ME!

I think it just randomly shows up in stores, but I found out that the more often you check a store for new stuff the less often they update their stuff. (might just be a "watched pot never boils scheme" but...) I think that it is required for you to be away for a game day or two before they resupply. I'm not sure as to the actual time.