[c-nsp] advertising a route not in IGP

[Jeff Bacon]

This is probably stupid, but I've pawed the books and I can't find a
decent answer. 

I have two meshes - a "vendor" mesh and an "internal" mesh, both EIGRP,
different ASes. 

I interchange BGP with vendors off the vendor switches. 

The internal IGP has a bunch of routes. The vendor mesh has a ip eigrp
summary on its interfaces towards the internal mesh that aggregates the
whole into a /16 (10.200.0.0/16). 

One vendor I need to connect to, I need to advertise a specific /24
(10.200.16.0/24) to the eBGP neighbor. OF course BGP won't advertise the
route to the eBGP neighbor because the /24 isn't in IGP, only the /16
summary.

I can't just set a static null route for the /24, because that would
screw up all traffic going to that subnet through that switch. 

I can't just pull the EIGRP summary at the boundary without causing all
sorts of other fun. 

I don't know of a decent way to "leak" the one /24 past the EIGRP
summary statement on the interface.

The vendor can't accept the /16.

Is there any way I can 
a) convince BGP to advertise the /24 to its peer? 
Or
b) somehow create a /24 that's slaved to the /16? (I don't care if the
/24 is redistributed through the vendor mesh)