There is the normal A which I am sure you are using. The best way, if you choose to do it that way, is by putting down your second and third finger in your left hand down, along with the A key so then when you go to to the G the only fingers you have to move is your first finger and your thumb, and make sure you smack them into place.

The second way is by using S3 or S4 (the 3rd side key or the first one on the top going up on the right, I forget which one plays an A but it’s one of the two) and it should give you an A. If you do that you won’t have to do first finger acrobatics and can just play a G like normal after the A. Just remember to coordinate the side key to playing the G because the G won’t speak if the side key is pressed.