Recently I traveled to Germany and Austria for 3 weeks, and these things I found at the Dollar Tree were very helpful: (1) in the Kitchen section, I found a set of 2 Microfiber kitchen washcloths which I knew from experience would be great for shower washcloths (in Europe you seldom get a washcloth, just a towel.) Every night after use, I just gave it a good rinsing out, and a squeeze, and hung it up to dry. (2) I found a set of two 3-ounce squeeze bottles for hair conditioner (they sell a set of 4 bottles at another store for nearly $5! ) and (3) I found a medium sized laundry bag that weighed almost zero, in case I had to take something out of my suitcase for the weight limit. (4) I bought a beach ball to inflate as a foot rest - worked GREAT at 3/4 full, but I looked sorta stupid blowing it up.
And here's what I found at Walmart - you're going to laugh - in the bathroom mat aisle, I found a memory foam bathmat that was very small (maybe 14" x 24") and weighed literally 3 ounces, but when folded in half, it was a great soft seat cushion.
What have you found at the Dollar Store?