This remote uses metal snap dome switches.

The original buttons are 5mm  round but the pads are large and can easily accept a larger dome up to 7mm. I recommend the 7mm cross type for a replacement

Common issue:

If buttons are hard to press, you can clean the buttons with Deoxit Gold G100L or replace them. Cleaning requires removing part of the sticker layer at a time (using a hair dryer for heat) to expose the metal switch. Apply Deoxit GOLD (not any other type) and stick it back down. Replacing them is easier, just peel off the old sticker layer and discard. You will need 7 peel and stick snap domes. 

If the remote is dead or the blue backlight stays on, that may be because the wifi module board has cracked some solder connections over time from vibrations. See the board closeup picture. The small raised board has two jumper wires going to the IC chip. This remote was broken and randomly either doing nothing or the blue LEDs would come on and not shut off. Flashlight button did not work. 

Also check the battery springs for corrosion damage from leaky batteries. You can clean them with sandpaper or a small wire brush if you take the remote apart. If you have Deoxit RED you can put that on the battery springs to help clean and prevent future corrosion.