Hi there!
If the netting you want is
just for the top of your run-to keep out hawks, etc.- we have an idea for you:
Fruit tree netting is available at nurseries and possibly at hardware stores, etc.
It is a durable nylon mesh designed to keep birds away from fruit.
We bought a 2 large packages at $14.- each [sizes come in S-M-L depending on tree].
Our run is roughly the size of yours.
We cut them into a few panels and lashed them together and to our fence with plastic tie straps at intervals, and nailed it with washers/grommets to our shed roof.
It also worked nicely around the apricot tree that grows up through our run. It is easy to work with.
We left a couple of feet draping over the fence and door as a protective apron from possible climbing predators and the more likely escapee-chicken.
I hope this helps!
Have fun!
p.s. someone on the forum suggested covering or partially covering my run* so that when it snows/rains, the chicks have a dry area... maybe this is something you could do while you're already working on it! [*tarp, wood, plexiglass...]