There is, it's called Airport Extreme Base Station...
You could:
* connecting an external antenna to it, or
* wireless bridging with yet another AEBS.
The extra cable sounds cheaper to me. You may try turning & tilting your ABS first into another direction, sometimes it helps.
In my garden, at one spot, my iBook looses connection within 18 feet with the ABS, the signal is going thru 4 walls however.