Cannot obtain until after getting all Golden Bolts on your first play through and amassing 250,000 bolts.
I personally used this guide and found it to be perfect.
http://ratchet.wikia.com/wiki/Ratchet_%26_Clank_gold_bolt_lo...After Obtaining all golden bolts and the 250k start a 2nd play through. Then when you get to planet Novalis you will find a teleporter next to your ship that will take you to the gold weapon shop.