I slept under a mosquito net one summer when I went to camp many years ago, and discovered that I much preferred that to sleeping in the old cabins with the gaps in the floor where the spiders and mosquitoes that got in could get at you all night. With the net, I could thoroughly inspect my small bug free zone every night for intruders, and once I tucked it under the mattress ensuring that nothing could sneak in, I got some of the best sleep I've ever had while camping.
Finally I went to Hobby Lobby (love that place) and got 8.5 yards of 1mm tulle netting in brown for about 9 bucks. (1 mm holes are small enough to keep out mosquitoes, but they are not small enough to keep out "no-see-ums" such as black flies and midges. You would need fabric with holes that are at most .6 mm for that.) It was what was left on the bolt and I figured that should be plenty. I came home and found this pattern. Fortunately, I had a zipper from when I deconstructed a kids beauty and the beast sleeping bag last fall when I was experimenting with underquilts. The zipper is only 5.5 feet long, but I figure I only need to be able to get in and out of one side anyway, and zippers are freaking expensive! You might be better off buying a cheap sleeping bag from Walmart just for the zipper if you decide to do this too and don't have one laying around in a closet somewhere. Or check a thrift store.
It's still a work in progress, but I feel great knowing that I could pull off an overnight trip soon now without much difficulty. Assuming it doesn't rain. A DIY tarp is also high on my to-do list.