Im on Nar shadaa and have gotten 2 of the 3 lightsaber parts from telos and Visas, where is the next one (Nar Shadaa is my first planet after Telos)?

You want to find Lootra and Aaida in the refugee sector, and complete their quest one way or another.

There is also a second way... there is a Hutt on the planet who has a storage room guarded by Kath Hounds. If you figure out a way to get into the storage room, then a piece can be found in there.

If your pc is darkside, it's easier because all you have to do is kill Lootra and you get a lightsaber piece. Lightsiders have to finish two quests in order to get the lightsaber piece from Lootra. You can loot Vogga the Hutt's storeroom for the piece as well. You'll need stealth skills. You'll have to go into the Flophouse and approach the two aliens in the first room using stealth. After overhearing their conversation, you'll take the appropriate measures. You'll also have to get the Vogga's dancer quest. Make sure you overhear the conversation first and get what you'll need before you begin the Vogga's dancer quest. After getting the dancer quest, you'll be transported to Vogga's place, where you'll be able to complete the quest. Good luck.

I suggest getting the lightsaber pieces from Telos, Visas, then Vogga's storage room. That way once you get around to Lootra instead of a piece he'll give you an extra lightsaber (single or short). That way you'll have two sabers instead of just one.