A Centrepoint Trading Station would be in a system and not on a planet. I don't think there are any in the galaxy, but if there are, the location may be on the Centrepoint Spacestation Website. Or you can send Togan Jano a dm and ask him.
There is only one Centrepoint Station (it's not a trading station, it's a unique station). It's located in the Corellia system if you want to take a closer look (from the outside)
“(Its not a trading station, it's a unique station.)
- Togan Jano ”
Yes, but you are able to access the market from inside one. That's besides the point that the only one in the galaxy isn't public. Will it ever be public?