Seems very rare but I just bought a few pieces from them

Yes if you are high enough level and it is a hit and miss. I have bought numerous parts from them none of which were X-01. The highest they have offered me is T-60 with the lowest being T-45

So theres no place in commonwealth were I can find a full suit of x01?

court 35 assuming your a high enough level

You can find bits and pieces, once your level is high enough and then you complete it.

My suit of X-01 power armour I actually scavenged. The primary suit minus the right leg came from the National Guard Training Yard because i was high enough level. The right leg believe it or not was loot off a Raider. He was using it on his power armour

I bought this suit from them as well.

However the paint scheme I bought from them does not appear to work.

https://www.youtube.com/watch?v=GJea1rWiGNM.