Is your damaged hyperdrive motivator slowing you down? Is your flux capacitor going all wonky? Do you have a clue what any of this means? If so, you should shop at Active Surplus, the city’s best—and cheapest—source for electronic spare parts, from fuses to wires, AC adapters to cable. If not, there’s still plenty of other cheap, practical stuff you might recognize: light bulbs and paintbrushes (all 50 cents each) or medical supplies, including health care booties (two for $1), suction catheters ($1.95) and dental tools. But mostly it’s hard-core Mr. Fixit stuff: motors, gears and transformers (usually less than $10).