The Empire of Dirt Workshop BH2-OBL Oblique Accessory Kit
There are multiple ways to add oblique capabilities to a BH2 microscope. The BH2-OBL accessory kit from the Empire of Dirt Workshop is one option which can be made using just about any 3D printer.

Click here for the PDF describing the BH2-OBL Oblique accessory kit for the Olympus BH2.
Click here to see the ZIP file containing the STLs for the BH2-OBL.
Click here to see a video showing the BH2-OBL.