I cannot be on the river without polarized sun glass, water, sun screen, forceps, gink, strike indicators, splitshots, and tippet (3x, 5x, 6x). I put all of this in my AMAZING sling pack that is made by magellan. It is 25 and will hold everything you need, honestly for the price I dont know how they arent sold out all of the time. The link is below, literally one of the best items I own AND Jerry's fly box will fit perfectly in it (trust me I know)

Academy - Magellan Outdoors™ Sling Pack