Other than a repeater (an AP device in trepeater mode), your only only choice would be an external antenna (as in "not built into the AP antenna").
If the flavor of 1300 you're using doesn't have external antenna connections, you're pretty much stuck. You'll need either another AP(as a repeater) or another pair of APs (with external antenna connections).
You may be able to re-position the APs ... perhaps the problem is the signal pattern being deformed by local "features" in the walls, ceiling, or other sturcture.
Try standing them off from the wall or ceiling a little further.
One other thing you can try, and this is just short of "Wireless Voodoo" would be to fashion a reflector at each end to further concentrate the RF in the desired direction.
It is rumored, and it DID work for me to some degree in the Lab, that a CD (like an audio CD) happens to work as a reflector.
You'll need to have someone at the other end watching signal strength while you adjust the distance of the CD behind the AP to maximize the effect.
Any ungrounded metal surface should work, so if you're into experimentation, it may save you the money (but Time is Money too, right?).
Good Luck
Scott
