Once you reach Sanctuary, there are 10 different places that Michael Mamaril will be located. Every time you enter Sanctuary he will have a different gun/item for you. You can either travel to another location and then back or Save/Quit and then Continue to get him to give you a new gun/item. You just have to find him, this will make it easier, learn the locations and make a circuit/loop.
1) By the news stand in the center of town 2) Inside Dr. Zed's "office" 3) Up the street from Dr. Zed's, at the top of the stairs(past claptrap's storage) 4) Lower level of Scooter's garage, under the stairs 5) Inside the Crimson Raider HQ, walk straight in, you shouldn't miss him 6) Down by Marcus, not the vending machine, but the actual Marcus NPC 7) By Crazy Earl's door 8-9) Inside of Moxxi's - 2 possible spots * By the slot machines * By the piano, in the room that Sir Hammerlock faces 10) By a dumpster - go down the large steps leading from Moxxi's, keep going a little past the steps that lead up to the center of town, he'll be on your left in a little alcove.
He didn't spawn for the longest time after Sanctuary took off; then right before my friend and I left to finish the game, we found him at Zed's. --- Compromise`Conformity`Assimilation`Submission Ignorance`Hypocrisy`Brutality`The Elite///All of which are American dreams
After the change, it seems like he spawns maybe 10% of the time. I was reading in another thread that he wasn't supposed to spawn every time in the first place. Apparently the 10% is the way its supposed to be, but the first Sanctuary map has a glitch or something. When it changes it becomes a new map and the glitch isn't there anymore...
Not sure if that's true or not, makes sense though.
Also it could have been the developers way to give you access to a decent gun(s) earlier in the game. Then once the story progresses you don't need that help as much so maybe they lowered his frequency...?