"You boldly enter our space! Approach this Dreadnought as though it were a recreation base and then play the dumb hominid? Who do you take us for, Captain... Spathi!?"
Instead of telling you where to find it, I'll give you some hints, from which you should be able to figure out the rest yourself.
"Sa-Matra" is Ur-Quan for "Great Trophy" -- it is the trophy over which their Doctrinal War is fought, for the faction which possesses the Sa-Matra has the power to make their doctrine reality.
Few know much about it, for most of those who have seen it didn't live to tell the tale. Two of your old allies from the first war were brought down by the might of the Sa-Matra, and are now slave-shielded together on a planet under the star of Procyon. Seek them out and talk to them. Caution: They may be guarded by battle thralls (although these are very easily manipulated, if you know what motivates them -- you can use the same device to manipulate them as you can use to talk to your trapped former allies).
As for its location -- since it is the most treasured possession of the Ur-Quan, it is zealously guarded near the centre of their sphere of influence. To learn its exact location, you need agents that often travel in Ur-Quan space. The Zoq-Fot-Pik live in the outskirts of Ur-Quan space, and have small, fast spacecraft that they use in scouting and information gathering missions deeper in Ur-Quan space. If there is something in Ur-Quan space which is conspicuously well-guarded, they will be sure to know.
Logged
Any technology distinguishable from magic is insufficiently advanced.