Heya,
Nice looking Damascus pattern. If sending the knife back isn’t an option, here’s what you could try:
Grab a 1/16” drill bit and hold it over the current ball to get a sense if the current one is that size or smaller. The idea is to file flat (carefully) the ball, center punch it, and drill it out. Then figure out how big you can make the new ball based on how much room you have on the lockbar. You don’t want to leave thin walls. After you decide what size hole you want to make, be sure you can order a ball bearing of the same diameter. Then drill your hole so that the ball bearing sits slightly more than half-way down into the hole. Once seated, use the punch again to swedge the ball bearing into the hole. One dimple should do. (Look up installing a buffer tube in an AR-15 for an example of what I’m talking about). Last but not least if the hole is still too large and you have lots of play with a closed blade, you could try adding weld (solder??) to the hole and making a new, smaller detent. Good luck and post pics!