My right bumper isn't working

9 out of 10 times its the sensor, not the button itself.

the only way youre going to fix it is by opening it.

Most likely to fail component is actually the small, thin and uniquely shaped flange that activate the right and left bumpers. They are slightly paddle shaped and extend out from the oddly shaped bracket they are a part of on a narrow neck that appears extremely fragile. Their known longevity is a testament to the design of the whole controller as they seem to last far beyond what one would assume. When they DO break however, the bumper is totally useless and since they are only a piece sticking out of a larger whole (and Valve no longer makes these controllers or parts) to replace it is an exercise involving more parts and areas than necessary, cannibalizing another Steam controller, or desperately searching for an improbable find online. Crafting a replacement is far more likely an option and this has its own issues.. There is a youtube video where a guy uses a tape measure for its type of metal material as the source for the creation of a replacement... I recommend it if this is what you are dealing with.

That's the trigger mount. Search "steamworks controller cad release" . If you have a 3d printer you can just print a new piece.

Look for the files:

ZIP archive for left trigger mount

ZIP archive for right trigger mount