Humidi-Grow trays are useful & versatile. As their name implies, they release humidity into the air. This is great for both the bonsai & the moss.
The grid is removable, and if your bonsai pot is shallow enough, you can add a little plant food to the water.
When it's time to water, lift up the grid, and sit the bonsai pot into the water. When done, replace the grid and the excess drips back into the tray.
Humidi-Grow Trays are available in six sizes. I recommend them strongly.