The USB riser cables came from China directly, I ordered them in bulk. There's really only one or two suppliers, last I checked.
There are a few guys who sell them on the forum here, you may look around the marketplace a bit and get lucky and find a local seller.
Was this the place:
http://www.aliexpress.com/item/PCI-E-PCI-E-Express-1x-to-1X-4x-8x-16x-Riser-Extender-Adapter-Card-with/944387438.htmlHere is our rig currently, adding a second machine into the chassis later today. Doing very nicely with temps running from 76-80 on the R9 290's. Had all sorts of fun with the MSI board and the risers (had to downgrade the slots to Gen1 to get it to boot) I also totally failed to get linux working (not got the linux skills sadly) Win 7 64 up and running a breeze tho. Getting about 430kh/s per card mining VTC atm. Chassis allows for 2 rigs, with a i guess enough space for 4 x cards per rig, but sticking to three per rig for now.
Rig design a work in progress, rather like the vertical mount idea with the fan blowing between the cards and board. Your design is very good and allowing a decent level of expansion, did you fabricate it yourself or build it based on existing shelving? Are you running 6 x cards on one board with 2 x PSU's?
http://farm8.staticflickr.com/7312/12187079633_953b9d7e1e_o.jpg