I just had a look at Edmund Optics.
They have mirror that may be exactly what you need, and it doesn't cost arm and leg:
http://www.edmundoptics.com/optics/o...mirrors/64457/
Other sizes:
http://www.edmundoptics.com/optics/o...t-mirrors/3150
The suface flatness may be the issue..
Surface Flatness 4 - 6λ
I am tempted to try this myself.
BW CCD camera (Vesta) should be OK for IR below 750nm