Base for this weapon is a Premium Mausser Particle Streamer. The gun itself can be bought from shops or found as mission reward. Further more, it can be assembled using instructions bought in Books Terminal. So getting the base is easy enough, but the same can't be said for the other parts needed.
Apart from the Advanced Hacker Tools QL, which can be bought from a Tools Terminal, must be at least 80% the QL of the Streamer; all the other parts must be at least 95% QL of the gun. The Compression Chamber for Chemicals and the Composite Barrel can be found in the Ranged Weapons Components Terminal. The Sheet of Curved Carbonum Plating is sold in Armor and Clothing Components Terminals. While all are shop sold, building a high QL one can be a pain because of the time spent shopping for the proper QL of items needed. Please also note that the QLs of the intermediate stages will be bumped up a bit if you have high tradeskills! Use the tradeskill window in order to adjust the final QLs.