I just bought an '05 Hawk and had a lot of trouble trying to find flush-mount alarms to replace the almost-expired CCI ones.
MTI industries/Safe T Alert is now about the only company producing 12V propane and CO detectors. I found that the "Classic 30 series" propane alarm fits in the flush-mount hole almost perfectly, and looks great, so I now have a new flush-mount propane alarm.
However, they don't (yet??) appear to make the similar 30-series CO flush-mount detectors. All their CO detectors are a totally different shape, and many are surface mount.
I do see however on their website that they make a COMBO LP/CO alarm that is listed as flush-mount, and virtually the same dimensions as the old CCI alarm (in fact in says it fits in the CCI cut-out). See http://www.mtiindustries.com/re6.htm
I will probably replace my almost-expired CO alarm with one of these dual flush-mount pieces. If I had known I would have just made a plate to cover up the old propane alarm, but now I'll have some redundancy in that system, which I suppose isn't a bad thing.
Hope that helps!
dc