I was looking at doorbell button part first and it is like $6 or nicer look is $10
I happened to find these two wireless doorbell system for very good price.
I just purchased Moko and see how it goes.
I think this is great price. review looks pretty god.
MoKo Wireless Doorbell, Plug-in Push Button with 36 Chimes, 5-Level Adjustable Volume, Battery-operated Transmitter(No Battery Required for Receiver), Work Over 900-feet(300m) Range, WHITE
1byone Easy Chime Plug-in Wireless Doorbell Operating at 500 feet, CD Quality Sound and LED Flash, 36 Melodies to Choose, White