Hi coolpick,
The only web sites that I know of that produce gauges is simkits and flight illusion, they are very nice but very expensive, you can find flight illusion gauges http://www.simw.com/index.cfm?fuseaction=dsp_products_list&mid=2&smid=146  here and simkits here http://www.simkits.com/

There is a book here http://www.mikesflightdeck.com/ that has instructions on how to build steam-gauge style instruments.

Have you considered using an lcd monitor to display your gauges on and place a face plate over the top and cut out the holes where the gauges are?
You can insert shallow rotary encoders so you can adjust things like Alt ,adf hsi ,etc..  on the panel and connected those to any of the control boards available.

Rhys