This 24V transformer is a good option. @Ken.S posted it earlier. Hook it up to the doorbell and plug it up.
24 Volt Transformer, C Wire Adapter Thermostat, Competible with All Versions of Ring Doorbell and Thermostat for Nest Ecobee, Sensi and Honeywell, 315" Long Cable 24V Transformer
https://www.amazon.com/dp/B07DJ7RHS5/ref=cm_sw_r_cp_tai_7HOAFb7DXN7DZ