use Subaru thermostat and water pump gasket.
Gates kits are widely used. rockauto and amazon for $130
or find a kit with water pump
2 cam and 1 crank seal are a good idea while you're in there particularly if yo'ure paying someone to do it since it would take the same labor to remove the timing belt if the $5 seal leaks in 2 years. get them from Subaru or make sure they're the higher quality "brown" material and not black.
Subaru if you're wanting top notch and want to spend for it. online retailers are about 20% less than local Subaru dealers. but you gotta pay shipping. don't ask "which one is cheaper" - as it all depends what you're looking for. Shawn from here can hook you up via retroroo with a genuine Subaru kit at a reasonable cost: