I agree with Greg, try the Subaru sealant. It's actually less than $2.00 per
container at my local Subaru dealer. I think I paid $1.39. I put in two
bottles due to the large capacity of our cooling systems.

I just cured a head gasket problem by using Bars Leaks Head Gasket repair.
It's more difficult than the Subaru product as you have to remove all the
coolant first, and it takes a couple of days. But it does work. I now have
no leaks and compression of 140-150 per cylinder. Who knows how long it will
last, but better than tearing the engine apart, in my book.

DON'T do the expensive mechanical stuff before you try the pour in sealants.
They work, and they don't clog up your radiator--unless you use the kind
that doesn't mix with coolant, in which case you'll turn the coolant into
green or orange jello. It may be that you have to do the mechanical work
anyway, but the pour-in sealants can't hurt.