A while ago I bought 2 24″x36″ softboxes on ebay. The package comes with a metal ring but without a solution to mount it on a lightstand and without a way to attach your hotshoe flashes. Time for a quick & cheap DIY hack.
In any DIY store you can purchase a couple of long M8 bolts & suitable nuts. With that attached to the metal adapter you now have a way for mounting the softbox on a stand. Adding 2 more bungee balls and your flash head fits rights in as well. Bungee balls are a bit harder to obtain in Belgium but I did already find some in the bargain section at Gamma. Otherwise check ebay.
I’ve added more notes on flickr if you click through on the images.