There is some important info missing here.

Things like...

What vehicle are we talking about here? Must be a Toyota, but model and year are useful if you expect us to remotely diagnose a problem without ever seeing the vehicle.

What fuse is blowing? The one for the turn signals, etc?

What circuit is the audio gear you added connected to? (Not a good idea if they're connected to the circuit powering the lights.) Did you do this yourself, and if so, could you provide a few details on what you did?

Does the fuse blow when the audio equip. is both on and off?

How much current does all this extra gear need? If you hooked a bunch of high-powered audio gear to any of the existing circuits, you shouldn't be surprised if you're blowing fuses.

I can say you'd certainly be wasting your money to have "this model" replaced even though I don't have a clue what you're talking about replacing. You need to understand the problem before going off half-cocked replacing stuff. Of course, if you want to toss stuff and buy something else, that helps keep the economy going.

If the Toyota shop couldn't find anything wrong with the switch didn't they try anything else? Were they trying it under the same conditions that cause it to blow when you use it? Did the fuse blow when they were testing it? Or does it blow only when you're driving down the road? If they can't figure out what is causing a fuse to blow that happens every time, they're incompetent and you should go somewhere else.