Do supermarkets sell ready-made broth stock for Lanzhou ramen?

Not available. Supermarkets you may find similar with instant noodles packaged Lanzhou beef ramen actually taste and authentic compared to far worse. The clear soup of beef noodles is broth and water, and the broth has been seasoned when the meat is cooked. If you like to eat fat, you can add more butter, so you can almost do it yourself.