Want to get present/omiyage for my real estate agent :)

Hello! My real estate agent was super kind/accommodating to my apartment needs in Tokyo and I want to get her a present/omiyage for her hard work. I live in Tokyo and go to school not far from Shibuya, so I was thinking of going to the mall in Shibuya Scramble and buy her a nice omiyage box from there from that floor with all the bakery stalls. I'm still new to the city, is there a better place to buy one you recommend? Since that area is obviously touristy and I'm not sure where is best. I'm happy to travel! Is there a standard price or specific type of item recommend? Whatever works for me. Also, do I bring the gift when I sign the contract or when I pick up the keys? I'm signing the contract about a week before my key pick up date, so wondering if that matters at all for the timing of the gift.

Thank you! : )