Upgrading a Wierd Sized PSU

[huhtristan99]

So I have an msi nightblade mi, which is a prebuilt small form factor computer. I wanted to upgrade the 350w PSU but it seems the PSU is a wierd size. I don't actually have a ruler right now to measure it but if I have to guess the dimensions are something like this

width ~10cm
length ~20cm
height ~6cm

I saw that PSU come in SFX size but those sfx size PSUs seem to be more square (12cm, 12cm, 6cm) whilst mine is clearly a rectangle. Does anyone know of any PSU's roughly the size of mine, or might fit in my case?

EDIT: So after some research I found out I have a flexatx psu, Which is a form factor used for low tier PSUs... so I won't be able to find a PSU that will fit in my case with decent wattage..... thanks msi :/

 

[BadActor]

The dimensions on these are 64 x 125 x 100. I would measure the dimensions of the OEM PSU to be certain.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817256063&cm_re=sfx_psu-_-17-256-063-_-Product

http://www.newegg.com/Product/Product.aspx?Item=9SIA6ZP3X94603&cm_re=corsair_sf600-_-17-139-155-_-Product