I'm sure this is dead obvious to most of you, but it never really occured to me before I saw it on another discussion forum:

If you're an android and find that you keep running out of support items in the middle of a boss fight, you can "plant" a bunch of support items by repeatedly dropping them in the boss room and letting yourself get killed (don't have your weapon equipped). The steps are:

1. Make a telepipe near the boss teleporter.
2. Enter boss teleporter.
3. Drop your support items.
4. Let yourself die.
5. Buy more support items at the shop.
6. Repeat until you've got enough support items to beat the boss in the boss room.

This way, you can pick up support items as you run out of them during the fight.