I cannot find beef ribs here in Albuquerque. Sometimes Costco has them, but they haven't had them for a few months. My brother-in-law told me he's had good experiences with the Crowd Cow beef short ribs, so I just placed an order. Cost is about $15/lb. for grass-fed Angus-Hereford beef. They have a $25 first-time-buy discount and free shipping after $99, so you can drive the price down a bit.
Can't wait to get some ribs on the smoker!
I don't know the difference between grass-fed and grain-fed beef, as I've never specifically bought one or the other.