There are small companies who make custom blade servers, a google search should bring them up. My only question is: are you looking for blades, or rack mount? Blade enclosures usually include space for 10 blades...I know newegg sells a pretty cheap rack mount case that you can put your own guts into, but it only has room for one PS... I ended up buying a dell poweredge 2950 when I found one for cheap, but it doesn't fit in my rack
MP