I am looking to buy an L bracket for my old Sony A99II will use this camera as my back up, but not finding a bracket anywhere so I can use it with the same ball head as my new camera
99% of available "L" brackets work with ARCA Swiss brackets. The only other clamp pattern I am aware of is Manfrotto. If that is the case, consider changing your ball head to be ARCA Swiss-compatible. There is a lot of choices for A-S "L" brackets.
I am looking to buy an L bracket for my old Sony A99II will use this camera as my back up, but not finding a bracket anywhere so I can use it with the same ball head as my new camera