Trigger replacement compound saw

This is where the aftermarket industry comes to the rescue. It does appear there are vendors still selling the original part, such as this one.

Bosch 2610911881 Switch-OEM-3915 B3915 Miter Saw-In Stock

But frankly the $145 USD price tag makes my jaw drop. Fortunately, other manufacturers figured out they could make money selling replacement parts far cheaper, such as this one for $27.

POWER TOOL SWITCH 3915ER – Eurton Electric Parts Store

These results are based on assuming you have the Bosch model 3915 saw, which shows the switch's part number as "Bosch SWITCH 2610911881". These examples were a result of an internet search using that as the search string; there are plenty of other results, so find one that suits you.