Just a follow up to my own posts, in case they can be of help to anyone else.
The Mirror Reflector Assemble from a Tri-Beam will work in a Tri-Image. This is good because a) the OEM part number for the Tri-Image is no longer available and b)it's $10 cheaper!
This part, like the original I would presume, is not a drop and go replacement. There are many adjustments that need to be made to the positioning of this part as well the other optics to get this set up correctly. Extremely thin shims may be in order as well. Put it in the calibration mode, block the green beam and adjust the reflector so that you get a complete red circle. Now gently turn each of the other two mirrors to ensure that your red beam is exiting the aperture correctly. Once this is done correctly, uncover the green beam and use the adjustment screws on its primary mirror to converge the two beams. Take it out of calibration mode and you're good to go! You may have to periodically make small adjustments, but usually only to the green beam which may be done from the bottom access panel.
If you get frustrated, put it back together and walk away. Come back to it when you're calm. It's touchy work and getting upset will only cause more damage. I also recommend eye protection from lasers when working inside these fixtures. Here is a link to some good safety info:
http://www.eyesafety.4ursafety...aser-eye-safety.html