losing antifreeze

[grc1]

97 geo tracker 16v auto 4x4

Hi , I have just started to lose antifreeze and none of it is on the ground. ( about 1qt every 20 miles.)

I believe I may have a bad head gasket.Also there is no sighn of anti freeze in my oil and no oil in my anti freeze over flow. I do have a leak down tester on order but it won't arive for another two weeks.

Were else can I lose anti freeze if my head gasket is ok?
Also can I get away with using a Ebay gasket set for fifty dollars or am I just buying crap?

Thank you

[the flying scotsman]

Heater core?