This is an alpha version of a 3d printed case for the Hackboard 2:

https://www.crowdsupply.com/hackboard/hb2

it is designed to have a 50mm fan mounted to the top. The fan plugs into fan connector on the board. Here is the fan: https://www.amazon.com/dp/B06XQDMMJ5. With the included small heat sink it keeps it cool enough. 

If you wondering how the top is held on, its nothing fancy, just some packing tape. Anyone else is welcome to take this and make is better. The onshape document is here: 

https://cad.onshape.com/documents/d1de8933bdaef2596545505a/w/6f0d72ea895e73aaea3c2e54/e/1d13104c8bc0b84642e350c2