You could try this for 12dBd (15dBi) of gain. Also, use 400 series cables if they'll be more than a few feet long. That L-com has a very narrow vertical pattern for such a wide coverage application.
http://www.rfvenue.com/rf-venue-24-ghz-microphone-helical-antenna
The pattern seems pretty close to the situation - 50 yard line from six stories up and some distance back. Last season I ended up with two access points in that spot, a few yards apart and with different antennas. And I put the access points right by the antennas, with very short cables.
BTW, our "custom windscreen" for Shure WL-184 has worked out pretty well after a couple seasons of trying other approaches. It's the plastic frame from the standard windscreen, then a layer of Meyer grill foam, then a layer of automotive headliner foam (comes with a layer of thin cloth glued to it). Sounds good, is quite wind-resistant, and nobody seems to care that it's about an inch in diameter.
