usually laptop keys breaking require a new complete keyboard, yes you could get it fixed by the manufacturer, but i don't recommend doing the repair yourself, i'd suggest calling the manufacturer, simply due to the fact that laptop keyboards usually have a specialized way they mount.
You can try but not likely, laptop keys last so long because they have a really nice mounting that usually when broken, might need a whole new keyboard installed, I'd say call your manufacturer.
I'd say try ebay... Keyboard's typically aren't too cheap and you will need one specifically for your laptop(or that series if some others use the same case) Maybe you'll get lucky and find some trashed laptop that still has a good A key for cheap...?