any recommendations on where to buy from
Are you sure you need to be messing around with your truck's brain?
If you are asking about using the OBD and Alfaobd, yet do not know where to buy these or that Alfa doesn't work with Apple phones. That includes one post (
@chopperman1) here suggesting that you do a bit more research.
I do not mean to insult you or anything...Yet, you can do more harm by messing with the brain.
If you need or want a trailer brake controller, research what are the best ones - either OEM or aftermarket. Then let the installer worry about programming your truck.