http://www.revisionfx.com/products/twixtor/downloads/
Choose the one you need there, and here are all the serials i got for final cut:
Twixtor FxPlug for Final Cut Pro
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Name = The Blade
Serial = b2c6TQYpt5nAKXxH
License = Pro
or
Name = The Blade
Serial = ejNqfBJu3IDcjg37
License = Pro
======================
Twixtor FxPlug for Final Cut Express
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Name = The Blade
Serial = OwOF7KKT5rJXy8gR
License = Pro