Hi Dave. I'm glad you posted and sorry I didn't have a chance to respond to your message.
All of the parts can be sourced from various vendors or some people here on buildlog. Your main vendors would be (here in the US):
www.inventables.com - makeslide and related
sdp-si.com - belts
McMaster Carr - hardware
lightobject.com (power supply, DSP if go that way, tube)
Misumi (20x20 rail and connectors)
And of course Amazon, eBay et al.
The plastic parts that were machined originally, can be 3D printed quite easily.
You can find all of my STL files here:
https://github.com/sshwarts/2.xLaserHowever, its easily to take the parts from the step files to generate your own STL files. In fact I really recommend that you should play with the design in your CAD program so you can see how everything fits together.
The cut are depends on your design. I don't remember what the original cut area is, but I scaled mine so I could handle a 18x24 sheet. This openscad file, can help you estimate what you need:
http://www.thingiverse.com/thing:12864What is it that you want to lasercut? You write that you're not happy with your CNC.
Scott