Hi Ken,
You can use this DIY automatic water refill method.
Get a big plastic bottle, drill or poke a 0.5 cm hole about 2" down from the opening, (Optional: another one about 2 cm down from the opening. If the water in the bottle could be able to flow down from the opening easily, then this is not necessary, it depends on how you possition the bottle).
Fill the bottle with water, close the opening with your thump and quickly place the bottle up side down into the 2" water in the water tray that you are going to put your pots in (I'm talking about those big trays that we could put many pots in). Now, to position it in the tray is tricky here, think of a way to position it. If a big pot is to be put in the tray, then just tie the bottle to the pot. The water flow out from the bottle whenever the water level in the tray gets lower the hole you drilled. Thus the water level will remain 2" for many days. You can use 2 or even 3 bottles if you are worry, but I think one bottle is more than enough.
Hope this helps.