If you are not worried about hawks, then you can construct a 4 by 4 wood box with door and latch and then put hardware cloth as long as you want it to be for the run; hardware cloth is safer then chicken wire.
well, even though it is a little expensive, (okay it is a lot) Omlet website has a TON of good coops, runs, and automatic doors and coop lights! their biggest coop holds up to 15 bantams and 7 large hens! There's also chicken fencing where u can create your own run.