Update: I bought a pair of Boston Boosts and Brooks Racer ST. Both are excellent fit for a narrow foot. I've run a few times in both shoes and can say that the Racer ST feels closer to the Supernova Classic. It has the narrow heel and midfoot, bit the toe box is flared a bit... the Boston Boost is narrow throughout the shoe and also seems to be much "less" of a shoe.. oddly, the Racer ST feels more like a trainer than the Boston Boost... and they both are much less stable than the Supernova Classic. Suffice to say that I'm happy with both shoes, but will probably do most of my easy runs in the Racer ST. Thanks to all for their suggestions!
DougC