Does anyone know that music name of when after Izumi beats up the Ed and Al, and where to download it if possible?

What episode number is that, as in, when they're older or younger?

If you're talking about the song that plays during and after the flashback where Izumi beats them up as little kids, it's called "Parting", Track 17 on OST 1.

If you're talking about the song that plays after she beats them up after finding out what they did, it's just a short piano arrangement of "Brothers". Specifically, it's a very abbreviated version of "Kodoku", Track 6 on OST 2.

P.S. I think asking for places to download things is generally looked down upon on these forums. I'm sure if you were to use a bit of Google-fu or ask someone privately, you would find what you need.

^Yeah, what they said. But I think you should just buy the OSTs.

Is the internet the only place to get the OSTs?

No.

I live in a small town (population of about 10 000) and I managed to find the third OST at the CD store here. You could probably even ask the store where you live to order it for you. At least that's totally safe. :'D