My Lexicon Alex is malfunctioning, where can I find parts?

I don't think it's broken. I think you've cleared some registers (probably number 5 from your description, maybe more) and now you're "us[ing] cleared registers as loop points." This means that you're looping 1-2-3-4 then back to 1 again. This is actually a feature of the Alex and it's awesome as long as you're using it intentionally :) If you don't know you're "using" it the unit have symptoms similar to what you're describing. It's possible that it is broken, but it's more likely that you're in this mode.

I attached a pic of my user's manual.

Also here are the directions as printed in the manual to clear or restore a register (i.e. a number spot on the dial):

1. Briefly press STORE/CLEAR until a minus sign (-) is displayed.
2. Press and hold STORE/CLEAR. If you were in preset mode, the register LED will go on, indicating that Alex has automatically switched to register mode -- selecting whatever register is indicated by the position of the REGISTER/PRESET knob. The "-" symbol in the display will flash, indicating that the CLEAR function is armed.
3. Releasing STORE/CLEAR will clear the displayed register. The display will flash briefly to indicate the clear was successful. (The ID number of any cleared register flashes when selected with the REGISTER/PRESET knob.)

Try Farnell - they have a export department who can send you the rotary selector switch and ship to your Rural area :)

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All the best