Update: This deal is available again w/ a new promo code and is now $1 less than the previous price.

VicTsingDirect via Amazon has Homasy 1000ft Wireless Doorbell w/ 52 Chimes & IP55 Waterproof Transmitter for $19.99 - $9 w/ promotion code ZE6UXSHV = $10.99. Shipping is free w/ Prime or if you spend $49 or more.