how or where to obtain alarm gems?

in the game Memoria Freese based off the anime Is It Wrong To Pick Up Girls In A Dungeon i want to continue the main story quests. but it requires you to complete this quest where you must purchase a voice for the in game alarm clock however i don’t know where or how to get the gems since they are not given as any reward in the story quests or available to purchase in game with the currency or for real money.