What is the thread size on the gear knob of a 2001 Ford Fiesta?

I need to replace the gear knob and I know it is threaded but can't find the size anywhere and don't want the hassle of buying one that doesn't fit

Check it out, Its probably (99% sure) that its a metric thread.
so get a metric tap and die set, and try threading one onto the shifter. You can get the right thread.

Measure the diameter of the threads. Then count the threads and measure the length. What you are looking for is the number of threads per inch.
If you can place a ruler beside the threaded part- count how many threads fall within 1 inch.

However- that should be standard. If you buy a gear knob for a 01 Fiesta- it should fit.