Hm? Well, they're sold in Empyria, smack dab in the middle of the Netheruniverse of course!! And perhaps other parts of the Netherworlds inside the Netheruniverse too.

But to get to Empyria, I guess first is you leave this school. Next is you hop on to the closest and nearest drifting object in space, and then finally just keep on drifting until you reach it! You can't miss it! And oh man, don't get me started on the sweets and snacks that just makes the visit to the main square just worth it! Soba noodles with magma green tea and top it off with taiyaki-- it's just simple things like that just makes everything worth going! And wait until you experience the more refined things!