Mark:
I've used the Wagner twin turbine for a couple of years, paid about $65US for it. It works fine, but I found I had to fiddle with the controls quite a bit to get the results I wanted. The tip tended to clog. One tip that helped a lot was to have the container at least 1/2 full of material to spray--this helped with consistency a lot.
But recently I bought one of these units from a low cost supplier here in the US. It does require a compressor, but I had a small 5 gallon unit that I was using with my pneumatic stapler (From the ratings, this would not supply the "required" volume of air). It worked fantastic. The gravity feed was more positive. The spray was finer and only directed at the canvas. The main difference I found was there was less over-spray in my spray room--the hallmark of using a HVLP sprayer. I would highly recommend this type of unit, if you already have a compressor. Also, you don't need the higher capacity compressor, if only spraying a few canvas' at a time. A 5 gallon tank unit has worked fine for me thus far.
http://www.harborfreight.com/20-oz-high-volume-low-pressure-gravity-feed-spray-gun-47016.html
