We propose a new augmented unit cell topology for realizing TM-polarized Huygens' metasurfaces (HMSs). They exhibit significantly enhanced performance compared to conventional designs. Each cell is isolated from its surroundings through the inclusion of perfect electric conductor walls between adjacent cells. These walls improve the performance of the HMS by enforcing many of the simplifying assumptions often used when designing metasurfaces. As a result, the proposed unit cells may be used to directly construct complex metasurface devices whereas HMSs designed using conventional cells will require laborious tuning and optimization in order to compensate for the aforementioned assumptions.