USB-Powered Disc for Beverage Warmer

I am looking to create a compact, USB-powered disc that will be used to heat food or beverages. The heat emitted by the disc should be just under 200 degrees, ideal to get my coffee, tea or soup at just the right temperature. The envisioned design for the disc is round and flat, and it should be small enough to be portable yet effective for its heating purpose. Ideal freelancer for this task should have experience in electronic product design and material selection, with an understanding of heat properties and USB-powered devices.
Ideal skills:
- Electronic design
- Material engineering
- Knowledge on portable heating devices
- Experience with USB-powered products.