Is it possible to convert a suspension fork to rigid by drilling it?
DO NOT DRILL HOLES IN YOUR FORKS

That would weaken them substantially and run the risk of them breaking under stress (e.g., when you hit a pothole). A broken fork will probably put you in the emergency room, and potentially the morgue if you're unlucky with vehicles nearby.

Hopefully, other answers will address how to fix your forks; worst case is replacement, which isn't crazy-expensive for rigid forks.