check out JensonUSA or Cambria bicycles. they usually have some old stuff that is new but last years (or older) models for as little as $80. I honestly wouldnt go above 80mm travel or it will change the geometry so much it wont be enjoyable to ride. my first fork was in 97, a rockshox quadra 60mm. basically 2 metal tubes, a rubber eraser for compression damping, and brake boss. now even a fork a couple of years old is an awesome thing. last time I checked Cambria had some 03 Manitou magnums that were 76mm travel ad about $60.