Well, that's a real lemon of PSU you have. Even if it were new and in perfect condition ~300w would be a more realistic rating for it.
Source: https://www.youtube.com/watch?v=aufZC7KIjhU
Anyway, it's listed as ATX form factor and has the same dimensions as the PSU I originally listed. So, if your current PSU fits, the FOCUS GX-550 should fit.
You could use the SGX-500 (which is way better than your current PSU) which is an SFX-L form factor and comes with an ATX adapter plate, but you shouldn't need to. If the standard ATX sized PSU fits, that's what you should go with.
Anyway, it's listed as ATX form factor and has the same dimensions as the PSU I originally listed. So, if your current PSU fits, the FOCUS GX-550 should fit.
You could use the SGX-500 (which is way better than your current PSU) which is an SFX-L form factor and comes with an ATX adapter plate, but you shouldn't need to. If the standard ATX sized PSU fits, that's what you should go with.