I had the isotope because I got it from the dead mr. RADical but I can't seem to find the isotope is there a way to get another one or am i screwed on that one... and if i do find it where is the thruster controls...

Wait, so you got the Isotope but you cant find it?

I ran across it a while ago and I thought I put it up thinking that I needed it for something ... I will check the shops to make sure I didnt sell it by accident. smh

Hm. I thought it was a quest object.

You can get the isotope from Novac too. Buy the key for those stupid rocket toys and five of them have enough isotope inside them.

buy the key for rocket toys?

You can't drop or sell the isotope, its either still on the dead body, or in your inventory. So go back to Chris and turn it in. IF you don't have it then five rocket toys from Cliff's shop will substitute.
But check in with Chris first.

maybe you need that other thing you need from old lady gibson?

From Cliff at the Dino Bite Gift Shop. There are also some in the gift shop at the REPPCON Headquarters and Mick & Ralph's has a bunch upstairs in a vending machine.

-Gunny out.

Lady Gipson has thruster controls.