Sensodyne does not have Novamin in the USA(insert conspiracy theory here). You'd either have to import it from a reputable supplier, or try an alternative like Apagard or Biomin F(both of those have to be imported too, but are more readily available).

Quick googling found a funny metastudy: "The articles from the database obtained for further review was N = 1. According to the study..."

I never heard of Novamin, but I used Sensodyne for years becase it tastes better.