When walking around the outside of Tsukiji, there are often many outside stalls grilling fish and seafood. Recently they have been combining uni with different types of shellfish. It is worth your time to walk around and check out the different stalls. To find this, it is not inside the Tsukiji fish market but they are on the outskirts. But save room for the uni combinations per the below.
#1: Oyster and Uni Grilled
#2. Oyster and Scallops grilled on a stick
#3. Crab and Uni grilled on a stick (no picture).
Enjoy your time in Tsukiji!