The Bevmo stores throughout California can generally get root beer kegs if you give them a weeks notice
Root Beer Kegs in Los Angeles Area
Hi-Time Wine Cellars
250 Ogle Street
Costa Mesa, CA 92627
949.650.8463
Haralambos Beverage Co
2300 Pellissier Place
City of Industry, CA 90601
Phone: 562.347.4300
Root Beer Kegs in San Diego
Keg N Bottle
Multiple Locations