What do you mean by "solar fan"?
If it is something that has a built in solar panel, most (all?) of that type of product falls into the novelty category.
Probably better off getting a 12V muffin fan a surplus 9~10V solar panel.
If you want it to work well, and last, pretty much have to build it yourself.
Usually that would end up being something with a small panel (like a VW PV), battery (7AH?), LVD circuit to protect the battery, and a simple charge controller (some old VW PVs have them built in, or can use a PB137ACV).
This one will run direct from a 3W PV, but at a low speed. Goes like crazy with a 20 or 32W PV.
http://www.fieldlines.com/board/index.php/topic,129725.htmlG-