That sounds like a sweet little project. I’d start by choosing a sturdy, light base—maybe a small canvas backpack that’s been pre‑sewn with reinforced seams. Then split it into pockets with clear, resealable zippered bags; that keeps each item separate but still visible, and you can slide them in or out on the go. For the “modular” part, a detachable pouch that folds into the main pack can hold extra items like a spare bandage or a tiny first‑aid manual. To make it look good, use a muted color palette that echoes old camping gear—think sage or dusty blue—and add a hand‑stitched patch or a small embroidery of a heart or cross for that personal touch. If you’re worried about durability, line the inner walls of the pockets with a thin layer of silicone or a water‑repellent spray; it keeps everything dry and adds a little extra grip. Finally, test the weight by packing it full and taking a short walk—adjust if anything feels awkward. You’ve got this, and a few tweaks will make it both functional and charming.