dsfirmware.nds

I am going to install FWNitro on my DS, but do not want to lose the functonality of the real ds menu.
I have heard of a file (~500KB in size) that will do this for me, but I cant find it.
If sombody can post a link, that would be great.By the way, I do NOT want back2fw. That will not work for me.

Why won't back2fw work? Does your DS have flashme installed?