Did you use pliers or adjustable wrench to shut it off?

Are you going to switch out the blue handle?

Looks like you need to buy a full replacement part if you can’t find just the handle with O-Ring and cap.

Your valve looks like the one below:

Videos related to this:

1. Fix A leaking PVC Valve Handle! Dont pay for a plumber! [04:51 | NOV 24 21 | MACH 1 TIPS] https://youtu.be/B3UYsMgeM1k&t=84

• Fix valve handle without diging or having to splice in a new valve.

2. Water well repair part 3, Bonus: how to repair a pvc ball valve [23:40 | NOV 12 22 | Scott Flory] https://youtu.be/Bnt4nPPfmmY

• Finishing up the rebuilding of the well, re insulation and repairing a pvc ball valve that started leaking.