I've searched multiple websites for the JP version of this game (both for the physical copy of it and and the rom), with no luck. Could only find the USA/EU versions. Any tips on where to get it?

The Japanese version is actually the second hamtaro for Japan, the name is Tottoko Hamutarou 2 - Hamu-chan Zu Daishuugou Dechu

Thanks so much that made the search way easier! Just ordered a copy