Hello Does the cooking -
Reblochon cheese - This rich and creamy French cheese is quite mild for a washed rind cheese, but it's complex enough to be popular with gourmets. The rind is edible, but too pungent for many people. Substitutes: Pont-l'Evêque OR Brie OR Beaumont OR Esrom OR Beaufort OR tomme (nuttier taste) OR raclette OR Port Salut OR fontina.
Tomme de Savoie cheese - This is a mild and pleasant French cheese that's semi-soft when young, firmer when aged. Substitutes: Tomme Crayeuse OR Saint Nectaire OR Muenster.
There are a few Tartiflette recipes on site, most use Reblochon. Ed Baines uses Gruyere. Another recipe says Les Deschamps cheese, or any cheese with good melting qualities.
Hope this helps!!!