The development of the next generation of K/Ka band ground communication systems relies on cost-effective, compact terminals that provide high gain and wide-angle beam coverage while controlling the pointing direction in two widely separated frequency bands (20/30 GHz). The authors have been working on dual-band mechanical beam steering solutions based on a single aperture, eliminating the need of having separate Rx and Tx modules. In our previous works, the 2D beam steering control resulted from in-plane movements (rotation/translation) of a single aperture. A renewed interest has emerged on an alternative scanning solution based on the Risley Prism configuration (independent axial rotation of two TAs). However, until now the focus has been on single band solutions. In this work we present a dual-band Risley Prism antenna, enabled by an ultra-thin dual band TA design. A dedicated in-house full-wave solver was used for a more efficient search of the unit-cell solutions space, which allows reducing 70% of the TA thickness comparing with our previous designs. Full-wave simulations show that the TA has a maximum directivity of 23.8 dBi @ 19.5 GHz and 27.3 dBi at 30 GHz and can scan up to 47 degrees in elevation with scan loss below 2.6 dB.