I'm not able to help with commercial sources in your area, but I get a lot of my timber from glaziers. They often replace doors which is a great way to get good wood for free, or a nominal fee. Most companies I have approached have been thankful for me to take them. The exterior doors are the ones you want. They often look in poor shape but have the best quality timber. Don't overlook the door frames either.
This Moxon vise was built from door components. The screws were turned from wood bought from a timber supplier.
Dumpster diving is also a good source, though can be difficult.