A food processor is what you want and Kenwood make very good domestic ones with decent motors. But they are a bit dear if you only want it for crumb, in which case it might be an idea to buy a budget brand.
A good tip if you want it very fine is to blend it, then freeze it, then blend it again.

I should add that I am really into cooking and have a Kenwood Food Processor but all you need is a blender. Less than £20!

It will produce finer crumbs quicker than a processing bowl and cutter as effectively you have twice as many blades and the bread is cut quicker and won’t heat up meaning that you can process very fresh bread too.

I use a Molineux that must be 30 years old now and it’s a superb bit of kit.

Three slices of bread ripped into three/four strips each and give the blender an occasional shake or blend at a 15-20 degree angle and jobs a good one!