Looking for a very tight binding ab/epitope pair

[WEDEL at vms.biochem.mpg.de]

This is my virgin posting; please excuse any errors in nettiquete.
I am looking for an antibody/epitope pair that bind very tightly with which 
I can stably link the antibody to an in vitro synthesized protein.  For my 
purposes the half life of the interaction under standard conditions would 
have to be more than an hour.
Does anyone know:
1) of such an antibody/epitope pair?
2) someone who might know?
3) a good place to look, or a better news group for me to post to with this 
question?

Thanks,
Andrew Wedel      wedel at vms.biochem.mpg.de