I got my tailwheel endorsement from a fellow Boeing employee here at Paine Field. He says he gets most of his CFI work by word-of-mouth, i.e. I don't know whether he advertises his services publicly at all, so I'll omit his name and invite you to send me a Private Message if you'd like me to get you in touch with him. But if you're in the Seattle area and want a tailwheel endorsement, I would highly recommend him.
He owns a Cessna 170 (as well as an RV-4). He's apparently quite active in the Cessna taildragger community (or so he tells me) and helps a few people per year transition to these old Cessnas. His 170 is docile and straightforward and easy to fly... and, most importantly, easy to taxi and take off and land. It is my current go-to rental airplane when I want to fly more than just one other person.
(I got tailwheel training from him when I thought I was going to buy a taildragger RV. Ended up buying an RV-6A with a nosewheel, but still glad to have gotten my tailwheel endorsement: it made me a better pilot, it gave me access to a nice four-seater when I need it, and it allowed me to experience flying a sixty-year-old airplane: Once you've left the ground, the 170 is not really any different from a 172. But landing a taildragger requires you to develop a very sharp sense for exactly which way the airplane is pointing, and that will make all your landings smoother, in any airplane. And it's always good to spend some time with a CFI who really emphasizes looking outside at where the horizon is and listening to the engine, rather than looking inside at the numbers. I can now land an airplane at night with no lights/instruments in the panel, which is a nice skill to have).