Favorite Budget Not-from-ci-accessory

I'm home from CICO 2024. (Sad, I know). One of the things I do is wander around and ask people what their favorite accessory is which was in some way a "game changer". I found that some people had pricey add-ons and some had budget add-ons. In order to not compete too much, I've made two threads. I'm encouraging forum readers to add a post to this forum thread. In this case, I'm thinking "budget thing", less than $100 for example. Think "got this at the thrift store or Walmart" type of things.

I'm also going to ask that you do not post an accessory type which has it's own thread, like Awnings, best fridge, or paper towel holder. Those have their own threads!

I'll start. I certainly have lots of sub $100 items. I have a 550, pretty sure this will not work in a 560. In a 550, there is just ever so slightly a gap between the mattress and the wall next to where pillows go on each side. For about a year or two, I would on purpose just place my e-reader and phone in that gap anyway, but other things would find their way into that gap as well. https://www.amazon.com/gp/product/B0743663D3 is what I bought in 2018 (according to my amazon order history); looks like it's out of stock, but if that's of interest, just find something similar enough that is about 9" long, 4" tall for the gap part.