Have a pet with 10 items in its treasure! I know how to get it, but how do I make my pets treasure size bigger?

random events, pet zapper and an item called Magical Keepsake Box. It's increase 1-3 spots of the treasure cheast

Thank you ;)

From the Millionaire Center in Centropolis, gives you 1-3 spaces, and the from the Cash Shop, gives you a minimum of 10 spaces :)

It's in random items (often xD, for me)