Theoretically, that lever unbolts from the selector shaft. Remove the inner wheel-arch liner to gain access.
That is the same ball that fell out on Vince's high mileage diesel on his way to Burghley house rally. A couple of tye- wraps saw him not only to the rally, but back home to Manchester.
That ball is a press fit /riveted union, so a dab of weld fixed it in place, but if the arm can't be removed, try a small carbide burr on a flexible drill drive, or remove the driveshaft.
You only need to remove enough of the splayed riveted end to remove the ball.
Tapping a thread and using a locknut should give a good and serviceable fix.

91 3.0 sei M. 4852 EXY Black
92 2.1 sed M. 5740 ECZ Sable Phenicien
92 3.0 V6-24. 5713 EXY Black
92 2.1 sd M. 5685 ENT Blue Sideral
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90 2.1sd M. 5049 EJV Mandarin
92 2.1sd A. 5698 EJV Mandarin
94 2.1sd A. 6218 ERT Triton
91 2.0si M. 5187 EWT White