Where to buy a live baby chicken? ?

They have animal flea markets that might sell individual chicks, but most places will have a minimum # of chicks they sell. Farm supply stores around Easter time usually have this big horse trough with a heat lamp over it filled with baby chicks. Also hatcheries sell them by the dozen. If you want just one, you might check into people that raise chickens for poultry shows. Poultry shows are a thing just like dog shows but they show chickens in them instead. Those people raise up different breeds of chickens and they usually have ones that aren't show quality that wind up as friars, or for sale as laying hens.

You can buy them at some feed stores that sell food for many kind of animals/

You CANNOT buy single baby chicks anymore.   There are places that sell them, but you have to buy a minimal amount.

For example, farm stores sell them, ussually in the spring..  But you have to buy at least 6.

Hatcheries ship them, but I believe it is a minimum of 10

You don't get chicks from a slaughterhouse. The birds there are either dead or about to be dead. 

You can get a chick from a chicken farm, from a pet shop, or from an agricultural supply shop.

Farm and ranch stores in my area sell them .