Mostly people are still just ordering them from Europe. Places like Seedsman or Sensible Seeds ship to the US, but obviously that's got some risk associated with it. There's a company in Oregon that sells them. They are called Southern Oregon Seeds. I haven't vetted the quality of their stock. The best options is probably the Seed Vault in Southern California . They carry a lot of well known brands, like Crockett, Gage Green, Loompa, Archive, Bodhi, and CSI Humboldt. Their website is http://www.holisticnursery.com/.
I've already order some csi humboldt seeds to holisticnursery.com. Never received and never get resent.. seems like a selective scam for EU orders. I asked 55 times about a strain availability, once the money was sent.. magic.. the strain was not available. Then my order was sent (with insurance) and hold by custom. The vendor won't claim for the insurance and never recent it. Very bad.. I would never order it from this shop.