Is that the shelf? If so you pass the refreshment kiosk on the way up but there is no alcohol served as far as I'm aware. You buy beers etc on the main North Stand concourse
There is but you need to go down half the stairs, out to the seats in the lower level and then back out of one of the other exits into one of the concourses. The downside is that you have to drink the beer there as you can't take it out past the seats back to N2A
Assume that's the shelf (was a bit suspicious of North Stand Upper), if so you can get down to the North Stand concourse without having to go outside. You will go past the kiosk at the top of North West but this does not sell beer even though it has a Harvey's pump (you can see the pitch from there) so don't join the queue just keep on going down.