OSBo used to use the same enclosure as OpenSprinkler. We don’t sell this enclosure separately any more, however, you can get the new laser cut acrylic enclosure for OSPi:
http://rayshobby.net/cart/opensprinkler/ospi_enc
and it should work for OSBo too because OSPi, OSBo and OpenSprinkler all have the same PCB size and the screw hole locations are the same.