I need an additional chime module also. TP-Link's website and FAQ's indicate that an additional chime module can be added. However, TP-Link does not sell separate chime modules - thus, depriving themselves of additional sales and profits!
On a similar note. I saw that the TAPO hub comes with a built-in chime. Likewise, I have read that TAPO devices are compatible with Kasa devices, so I purchased a TAPO hub so I could get an extra chime for my Kasa camera. THAT WAS A MISTAKE AND A TOTAL WASTE OF MONEY, as (contrary to what TP-Link has written their Tapo hubs are not FULLY compatible with Kasa devices.
TP-Link, if you are listening, please make the chime modules available for your Kasa KD-110 Doorbell Cameras! You'll sell a lot of them. Likewise, you need to clarify that your Tapo hubs are NOT completely compatible with Kasa products.