Look for a 2.4 kVA single-phase transformer with 277 V to 120 V windings. That's the minimum calculated size that will work, so you may have to get one slightly larger to line up with what is commercially available.
For current protection should I only need a 15A breaker in the 277v pannel, or should something be on th 120v side. My problem is the CODE makes it sound like I only need protection on the line side, but the MATH says that 15As on the line side is to large. I don't beleive they sell a 10A breaker that I can put on the line side, or do they?
I agree that the MATH is wrong for 15A on the 480/277 line side to protect a 20A 120V circuit. I am not sure where you got that requirement, but perhaps it was a maximum allowable rating? I also think that putting it on the line side is safer.
I am not sure who "they" is regarding to making breakers, but how about a fuse? You would need to make sure that your fuse had a sufficient voltage rating but this shouldn't be a problem. I just did a quick check from my favorite parts supplier and found a 5A, 500V fuse for $1.40 (USD).
I am sure that there are breakers in that rating range too, but they will be more expensive.
