You have several options.

Find the right part.

Make the right part.

Ugly Layout Fudge:

Use change diameter to select the diameter you
want for the new pad. Place a via where you
need the wiper leg.

Connect the wiper pad to the
via with a wire. Name the new wire and via with
the same signal name as the old wiper pad.

If you do not rename the via and trace you will
get DRC overlap errors.

There are many pots on the market, some of them metric and others in inches and fractions thereof.

The best way to make an already purchased part fit exactly on the PCB is making a new package.

Select any package coming close to the one you have (shape and orientation vertical or horizontal).

Copy the package by grouping it completely (including >NAME and >VALUE). Create a new package by typing the name of it. Anwer "yes" after the question if you really want to create a new package. Then paste the copied package and do the necessary changes like pin spacing, diameter and drill size, also pin numbering (if it differs from standard). You are also free to delete pads, since the package is not in use yet. Deleting pads is useful if the original part is scaled different from yours, mm to inches or vice versa.

Editing the shape of the package you should disable the 'pads' layer (17) for optimum results without erasing pads you didn't intend to erase

Save the "new" package and create a device using the standard pot symbol and use the package you've just made. Assign pin numbers and you're finished with the job.

Boncuk