I recently ordered this fanny pack from Amazon and I love it. It's ultra lightweight, but is roomy enough for my iphone, 3-4 poop bags, treats, and keys. https://www.amazon.com/Ultra-Slim-Running-Elastic-Belt/dp/B016XG39YI/ref=sr_1_2?crid=28WGOWDKZ132&keywords=fitters+niche+fanny+pack&qid=1559148615&s=sporting-goods&sprefix=fitters+nich%2Csporting%2C170&sr=1-2
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For longer hikes, I use a drawstring backpack so that I can carry some water and still be hands free.
https://smile.amazon.com/gp/product/B016XG39YI/ it's this one. We used to use kids spibelts, but he'd destroy those in under a month and we couldn't fit the inhaler. This is less stretchy and wider so it packs flatter and smoother. Plus it's less than half the price of the spibelt and has lasted longer.
I hope you have a great time!! I've been too many times for any sane person, so feel free to DM me if you need any help :)
I guess you need a lightweight running pack I would recommend this one https://www.amazon.com/dp/B016XG39YI Slim and lightweight