What is your budget? A lot of posts for retailers, but here are some links for Amazon (no referal link, not making anything on this).

Sensor kit (pi board, sensors, breadboard, wires, cables, microsd...no case, power, fan, heatsinks) - $135 in stockhttps://www.amazon.com/SunFounder-Raspberry-Modules-Sensor-Included/dp/B07896TMD9

RPI3B+ (board, case, power supply, video cable, microSD, USB reader, heat sinks) - $80 in stockhttps://www.amazon.com/CanaKit-Raspberry-Complete-Starter-Kit/dp/B01C6Q2GSY

RPI4B 4GB (board, case, power w/switch, 2 video cables, microsd, USB reader, heat sinks, fan) - $100 in stockhttps://www.amazon.com/LABISTS-Raspberry-Complete-Preloaded-Heatsinks/dp/B07YRSYR3MRaspberry Pi home automation sensor kit - $22 in stockhttps://www.amazon.com/KOOKYE-Modules-Arduino-Raspberry-Professional/dp/B01J9GD3DG

Ultimate sensor kit - $75 in stockhttps://www.amazon.com/Adeept-Modules-Ultimate-Raspberry-Guidebook/dp/B01M4OVDHM

If you have Target in your area, many of them stock Raspberry Pi 3B+ starter and ultimate kits for $80 and $90 respectively (https://www.target.com/s?searchTerm=raspberry+pi)

Pi3B+ Starter Kit - Board, case, power supply w/switch, microsd, USB reader, heat sinks, video cable

Pi3B+ Ultimate Kit - Board, case, power supply w/switch, microsd, USB reader, heat sinks, video cable, breadboard, wires, leds, resistors, couple sensors, GPIO break-out

Lastly, Best Buy also has many kits in stock (and for shipment). More than what Target has, but most not in stores. Pi 3 and 4.