Carlson Steelworks downtown...
You could also hit up XO Fab on here...He's got a thread going in his vendor section...There's quite a few folks that frequent the roads between here and where XO is located...
I got some from OnlineMetals.com and picked it up at the warehouse in Ballard. Called ahead and asked what different drops and randoms they had and was able to get a discount. They were cheaper than Everett Steel with a company account.