We're in the process of putting up a pre-fab run - but here in France, there seem to be a number of available options. The one we chose was from a place in the UK 
https://www.feelgooduk.net/product-category/galvanised-pet-cages-and-runs/  though I bought it through Amazon.fr to simplify the import stuff. (Getting trickier as Brexit looms...)
We opted for a 12 m2 model that has proven to be relatively easy to put together. The frame more or less snaps together. You have to cut the PVC coated chicken wire used to cover the frame, leaving an apron - though I think you would probably want to reinforce that with hardware cloth given the predators in your area. (Used to live in the Bay Area in CA.)
A quick look at the US Amazon site shows me that there are a couple of chicken runs available that look similar to what's available over here. Take a look and see what you think - maybe hire a handyman type to put it together for you.