|Rather than do the leg work for you, I'll give you a link to a company who's wireless products we've used here at my work in limited capacity.|
I suspect something like a wireless "long range client bridge" might be what you're looking for but definitely look through their stuff or email them and ask what they'd recommend you use.
Once you know what type of device best suits your needs, do some shopping around. Compare spec's and prices and find yourself a good deal.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.