I agree with $10 gift card (I like Target or Walmart, or something that you can spend the card the next day on food and get rid of it). Best Buy, Starbucks, or Amazon might seem more appropriate for the theme maybe, but I like practical.
Battery back-up is good too. I finally got one 6 months ago and I don’t know why I waited so long.
If you have time you can ask area businesses to donate some sort of discount coupon to a gratis/swag bag. Starbucks might have mini instant coffee samples.
Whistle, taser, mace.
Notepad and pen. This might not seem like a gift if there is going to be note taking anyway.
Mini umbrella, or one of those fold up bags that fit really small in your purse.
If you just want to go to the supermarket (easy) sleeve of cookies, microwave popcorn, nuts, dried apricots, chips, chip clip.
T-shirts, hand towel, beach towel, sunglasses, chapstick.