I know this is an old thread, but...
I'm putting one together currently. I'll add photos this weekend.
I recently became a 'certified pullorum tester' and for the most part, all you really need is a smooth, non-porous surface to do the testing on. Samples in the class were ceramic tiles, plates, plexiglass - you get the idea.. They had a 'pullorum testing unit' on hand, I believe it was the one available at
Murray Mcmurray, and I wasn't crazy about it because: 1.) It runs off of a plug-in light, which would obviously be an inconvenience if an outlet isn't available & 2.) It is absolutely overpriced. Basically, what you're getting is a plastic box that isn't any more durable than a stackable storage container (what I'm building mine out of), with a light socket installed and an etched piece of frosted plexiglass to do the testing on...
I'm using a plastic storage container from Rural King. It was $3 and I'll get a photo and the proper item information listed here in an edit soon. I had originally planned on using one of those battery operated "as seen on TV" light bulbs (
here) and I still may since they're only around $14 for a 2 pack, but I plan on testing out some push on L.E.D. lights - some of which are only a couple of bucks, but I wonder if the L.E.D. lights will be too bright and won't diffuse well under the plexiglass..
On to the testing surface. Plexiglass! You can get a sheet that is pretty much an ideal testing size for a little over $2 at Lowes. If your local hardware doesn't have frosted you can use a fine grit sandpaper on the underside (that you won't be testing on) to get the same effect. I'll either score it with an exacto or possibly mark out the grid on the underside with some sort of marker - I'll test both for preference.
If the L.E.D light works out and diffuses under the plexiglass, then realistically you could build one of these for $10-$20. In my opinion, despite it being on a budget, it is superior to the pricey units in that it is wireless. I don't plan on permanently attaching my light source, so that I can use the inner compartment to store relevant supplies when transporting..