Durin sector sells lvl 9 and 10 parts, After main quest events mardo sector sells lvl 8 parts and if I'm not mistaken Atropos sells lvl 7 parts.

where do i find atropos?

"north west" of Chemrock. there is a little mining outpost there, but you have to fix the lockdown first.

After a certain point of the story, a new area of Mardo opens up, with a new shop. That, and the one in Durin, are what you need.

Can you point me to this Durin sector please?

You have to have gone through the majority of the story before it opens up. You'll get there after

you escape from prison and join the revolution

There is a chain of missions from a prison official that you need to progress in, though you don't necessarily need to collect all of his bounties.

Ok, thank you very much!