There are sucker sellers. Suction cups are also called glass suction cups. Suction cups are used in many industries, such as sticking tiles and stone boards in decoration, and installing glass in doors and windows. Hardware stores opened near residential areas will definitely sell them, and those opened near industrial areas will generally sell them.
The reason why the sucker can't suck is that the sucker is aging. This problem will appear after a long time. If the sucker can't be vacuum, it will fall down. If the sucker is a replaceable surf pump, remove it from the pump, then scald it with hot water or boiling water for a while, take it out and wipe it clean, then put it back on the pump, and suck it to the fish tank wall immediately after launching. Or you can talk to the seller about a new sucker. If the sucker can't be removed, change to an updated surf pump with the boss.