build one!
I built mine. It works good for me. I had a GMC short box when I built it, and now I am back in a Dodge (short bed as well) so I had to mod it just a bit to fit the different dodge bed. When I built mine, I decided to go with aluminum, with plywood deck, and one-piece alum ramp. I bought the materials in Feb of '07, and with prices what they were then, I paid about $1300 for the aluminum, wood, lights, wiring, switches, plugs, turnbuckles and chain. I used LED lights, and internal chains with turnbuckles, I have some load/unload scene lights on top (nice when it's dark) and it's worked really well.
the other benefits to building one, is you can make it the way you want. I can put all kinds of storage under the deck, (rubbermaid totes with our gear in them) plus it's tall enough to put full size fuel jugs (with fill spout attached) as well. I have raised railings on the side (raised about 5"), but no sheet metal (I can easily shove snow off after riding all day) and two dudes can easily put in on or take it off.
If you want, I'll be happy to send some pics, just send me a PM with your e-mail in them, the file sizes are quite large, so it's better to use e-mail. I can also take some time and draw out what I built. I have some schematic sketches on paper somewhere, but they are pretty ratty. I would be willing to re-draw them, and fax to someone if you want.
PE