For the portals/holes in the mug you can put a ceramic or glass/clear plastic oval shaped tube and put it all the way through the mug, and to make up for the lost space from the portal tube just make the mug bigger! And maybe different styles like the test chamber and what the test chamber contains, also an overgrown/old one would be cool (and with the overgrown one maybe stylistic broken glass in the gaps of the portal would be really cool).