Personally, I don't think that Desert Ironwood needs stabilized. It's a dense tough wood. I get my wood from several places. Places like Jantz, Texas Knife, Alpha and USA Knive can have good deals on wood at certain times.
For other exotic woods, I buy from Ebay a lot. If you're patient, you can score some really good deals.
Bell Forest Products has a good selection of exotic and domestic woods. You can buy them rough and then send them off to be stabilized. Here's their website.
Exotic Knife Scales
Exotic Wood Group is another place where I've scored some good deals on all types of wood. Sometimes I'll buy the lumber and cut it down myself and then ship it out to be stabilized if it needs it. Hard, dense, oily woods I don't send out. Just a personal preference.
Culpeppers has awesome knife handles in a wide assortment of materials.
I buy from a few other places, but those are the main ones. You can also check the For Sale area here. From time to time, there are some good buys on exotic woods.