Looking for PSU that fits

[mrnarwhal]

I recently bought a Lenovo M91P from a friend for cheap and I'm looking to upgrade a few things. I've already doubled the ram and storage, but I'm looking to get a new gpu for the i5-2400 on it, to replace intel hd2000 integrated graphics. I wanted to get a good card so I figure I'll need a 400w PSU, but the model on my computer only has 240w, so I was looking to upgrade. The board is a Lenovo is6xm, and the current PSU is a fsp group inc model fsp240-50 sbv.
Unfortunately, I don't know a whole lot and don't know what PSU would fit on the board. I know its smaller than an ATX. The current one of the board fits pretty snugly and has the dimensions 7x3x4 in inches. Anyone know what form factor this is and what would be a good 400w or more PSU in that factor that's compatible?

 

[C12Friedman]

The PSU appears to be TFX form factor but I'm not in any position to recommend one since I have not seen any legitimate reviews for those.
Have you considered changing the PC case? A midtower case is not too expensive (avoid the ones that come with a PSU, the PSU's in those are almost always junk) and opens up the ability to put a standard ATX PSU inside

 

[Vic 40]

Is there really a need to post this twice?
http://www.tomshardware.co.uk/answers/id-2681111/small-psu.html

 

[GhislainG]

If it's TFX, then 350W seems to be the maximum that's available: http://www.newegg.com/Product/Product.aspx?Item=N82E16817151115