Amazon has the Samsung FIT Plus 256GB USB 3.1 Flash Drive (MUF-256AB/AM, Gunmetal Gray) for $20 with free shipping on $35+ or with Prime. List price: $25. Features speeds up to 300MB/s, reliable and secure storage for your photos, videos, music, and files. Water/Dust Resistant: Yes; 1m depth 3% NaCl salt water, 72 hrs, water proof, shock proof, magnet proof, temperature proof, x-ray proof.
Has excellent Amazon Reviews.