This is the time of year to go collect it wild. And the vulgare in the name
Hordeum vulgare means "common", so it's out there and you
should be able to find it in many locations. When I lived in Colorado, the open space at the end of the subdivision had barley that was naturalized. Every spring it would grow back and in summer there was a crop of heads ready to harvest. Keep your eyes open to the fields you pass by in your travels and you will probably come across some.
I'm keeping a diary/logbook of all the plants in the area that I might have a use for in the future. Some are wild like the daylilies in a ditch by the side of the road, there are formerly domestic plants, like the
apple and peach
trees that are in a lot that is now vacant, since the house was torn down, and then there are landscaping plants like the the plum and the bald cypress at the shopping center. I think there was some barley last year near the pedestrian overpass over the freeway; I'll have to check that the next time I am in that neighborhood and see if there is any this year. Collecting from the wild is a tactic that Permies should avail themselves of, but these days, even that is not a guarantee that seeds haven't been "messed with".