in that case, i recommend switching out the light switch so it's a combo light switch and outlet in one. then you can use the external transformer.

to do straight 120v, you're looking at a more expensive transformer:

https://www.amazon.com/dp/B07L9X9V57

but you'll need to also extend the light switch out with an extension ring (since 120v wires can't be exposed.) it'll just look really ugly to have the transformer and the extension ring sticking out at every location.

Much cheaper to just change out the light switch with something like this:

https://www.homedepot.com/p/GE-All-in-One-Toggle-Switch-and-Single-Pole-Outlet-White-59797/203744889

or this:

https://www.amazon.com/Leviton-T5625-W-Combination-Tamper-Resistant-Receptacle/dp/B002LSI72M

Then you have an outlet you can plug into.