On Popeye, you have a center storage area for backpacks. JPRA has lockers that are around $1 per hour.
If you want, you can go to the Hulk or Dueling Dragons and store your goods there. The lockers are free on the Hulk for 75 minutes to 2 hours and Dragons from 45 minutes to an hour. Each additional 30 minutes are $2 per 1/2 hour.