I have played through this level a couple of times, and I have not found any equipment stores or other ways to get equipment. What do I have to do to get the equipment in this level?
This one's a bit tricky.
First, go and find the two treasures in the north. Ignore the earthquakes for the time being. Once you've found both treasures, return to the area with the destroyed vilage. Circle around the eastern craters near the destroyed village, and approach the southeastern crater from the east.
When you step into this crater, the Time Goddess will notice some treasure in it.
Then, you should finish the level normally, by stopping the quakes, saving the village, and then taking on the Evil Lord. After you've cleared the level, you'll get 3 additional pieces of equipment. I believe these are the bits of equipment that the Time Goddess took from you from the previous three levels.