Import Experts on Ebay - they have the best prices on decent quality. some of the cheaper kits on ebay seem less robust, having installed multiple sets from various suppliers.
They will also allow you to contact them and add or take out any parts you want and essentially create your own kit.
While you're in there around the timing belt, for a reliable 100,000 miles you'll want to:
replace timing belt, pulleys, and tensioner
reseal the oil pump (one oring from Subaru and anaerobic or appropriate RTV sealant around the pump case)
replace crank seal and 2 cam seals
replace the water pump - use a Subaru water pump gasket - the aftermarkets are cheap cardboard junk and prone to leak
replace the thermostat - use Subaru or XACTA from Stant, the others are visually inferior.
If it has a plastic rear separator plate you'll want to replace that and probably reseal the existing one if it's metal. They crack/leak and it's easily done with the engine out for a clutch job.
Rear main seal issues in Subaru's are nearly bullet proof and never leak so make your own call on that. Just be sure to install it exactly right and use a Subaru or Subaru quality seal - they are less forgiving than any other seal on unclean installs.