My left button on my flipper zero stopped working and im wondering if there is any way I could replace it or have someone replace it.
The small tactical buttons are pretty common and easy to replace, being a rough clumsy orc like me, i have not manged to permanently break them yet, but i do expect to break them in the future at some time, especially since i also like to play snake on it and I am not the most subtle user on average, especially if its my own hardware i do tend to use the max out of it . 
If you need to replace them anyways, maybe wanna look into the ones from pioneer used in cdj’s , they are built to be abused hard for a long time and i think it is the same form-factor Worst case if they are more thick you might need to sand a mm of the case/button setup but looking at it, it really seems to be a close fit to the pioneer ones. And these you can step on 50 times a day for 10 years without worrying.
So I sorta hope it is more easy to fix for your situation , and it might be a connection issue that could be resolved easy by reconnecting the board, but even if you need to replace the button it self, it is not the worst part to fix and only a soldering station with a fine tip will do, you do not need fancy SMD heat guns for those buttons. Any local with a bit of experience of breaking/mending electronics and soldering should be experienced with buttons alike.
But i do encourage to go for a DIY fix,since replacing just a couple of buttons/connections is a lot easier then it might sound, and for a couple of bucks you could do it yourself while enjoying the the repair and be proud on your own results.It will at least help you gain 5 levels on dolphin stats.