You may find that used shipping crates are cheap and easy to find where you are, especially since you're in a coast state. Add legs, put a hinge and latch on one side for access, a ramp and pop-door, some vents, paint the outside and clad the roof. The crates that motorcycles come in seem like a...
You might look at some of @Shadrach's ones https://www.backyardchickens.com/articles/shadrach%E2%80%99s-multi-coops.74344/
I'm pretty happy with having multiple tiny coops and adding more as needed. I haven't had trouble with our current arrangement of two small coops in one big run.