Gundam has had references to Bandai, such as crates or buildings. One of the SD series actually makes it part of the action- hero and villain are fighting, smashing up buildings as they go. The hero stops the villain RIGHT before they smash into Bandai HQ.
Probably also worth mentioning that alot of the really kid aimed Gundam manga are VERY open about pushing kits, making it part of the plot and having the cast be near obsessive over the hobby.