Hey, it's not explicitly hit points, but Shape Soulmeld (Rageclaws) is not a bad choice. It's sort of like getting 9 or 10 extra hit points.

If he goes with Azurin Barbarian, he could invest his 1 essentia into the rageclaws so that he can drop as far as -12 hit points before he dies (at -13), still being unaffected by his condition.