Hovercontrol has one at their site-
http://hovercontrol.com/ At Hovercontrol, go to the File Library.....
Find the AP in FSX Panels and Gauges
If you need an instruction manual, download the FS9 version, 'HC075DI_AFCP_UPDATE', from FS9 Panels and Gauges, page 2.
I used the fs9 version in FS2004 and it worked well. Haven't tried the fsx version.
Dave
At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation.