Thonky.com's EarthBound Walkthrough

This page lists the locations of vendors who sell Multi Bottle Rockets in EarthBound.

Scaraba Desert Arms Dealer

The first time you can buy Multi Bottle Rockets in the game is in the Scaraba Desert after you have passed through the Pyramid. North of the pyramid exit, you find a vendor with a camel. Talk to this merchant to purchase Multi Bottle Rockets.

You can buy Multi Bottle Rockets from this weapon seller when you first encounter him, but there is a more convenient location to buy Multi Bottle Rockets in the Deep Darkness.

Deep Darkness Arms Dealer

You first reach the Deep Darkness after you find the Yellow Submarine in Dungeon Man. Go south from where the submarine drops you off, then keep going east until you find the arms dealer. He might be underwater in the deep water, so if you can't find him, look for a moving shape in the water and talk to it. This shop sells Multi Bottle Rockets.

This weapon salesman is the most convenient location to buy Multi Bottle Rockets, because whenever you teleport to the Deep Darkness, you will arrive on the strip of land north of the arms dealer, and you can just go east and south to reach him.