If that truly is a HDMI In port than You would have to get a USB to HDMI or USB to VGA adapter. It would then drive the monitor.
Something like these http://www.newegg.com/USB-Display-Adapters/SubCategory/ID-3046?Order=PRICE
If I were You I would get a USB3 version as it could benefit from the extra speed.
- Compact, USB powered adapter provides the easiest way add a secondary or additional display to your PC
- Completely external device offers a simple upgrade solution saving the cost and hassle of upgrading the internal video card on your system
- The ability to use multiple adapters (up to five) provides a scalable display configuration for future expansion
- Optimal performance at 1680x1050 and ideal for use with 20" to 22" monitors or smaller
Be careful. I think many of the items in the first link will only work with compatible smartphones (i.e. all the ones that have MHL in the name).
You are on the right track. There are USB graphics adapters out there. I know because I use this one to add a second external screen to my MacBook Pro:http://eshop.macsales.com/item/NewerTech/VIDU2DVIA/
Just be aware that USB graphics adapters CANNOT handle graphically intensive tasks well or at all (i.e. the big example is graphically intensive games). They also generally cannot deal with HDCP protected content (for example, my TV shows and movies bought through iTunes will NOT play on the monitor connected by way of the USB graphics adapter).