Earlier this year, Banpresto's Ichiban Kuji goods lottery raffled off some interesting (and practical) Legend of Zelda products in Japan, including a Hylian shield shoulder bag and a Master Sword umbrella. You can still get those items on eBay (for exorbitant prices of course), but I don't recommend it because this glorious mass market Master Sword umbrella is now available to pre-order for $34.99 shipped. Apparently, stock will be limited so you'll want to grab it sooner rather than later.
The picture above is only a rendering, but you can see that this new version will feature an elaborate scabbard and can be worn on your back like an actual sword thanks to the strap. It measures 36 in (D), 21 in (H), so it's actually sword-sized. Plus, the umbrella canopy will have a fancy Triforce design.
I highly suggest getting one of those new fangled electronic Legend of Zelda Ocarinas (purists can always stick with the ceramic versions) and playing the Song of Storms just so you have an excuse to use the Master Sword umbrella. And if you want to continue to upgrade you gear when compared to the Banpresto lottery, you can always pick up a Hylian Shield Backpack for a reasonable price.
But why stop there? There is a huge line of official The Legend of Zelda items that you can use for everyday cosplay - including new Breath of the Wild products. Personally, I think a classic or a Breath of the Wild cosplay hoodie would be great on a chilly, rainy day. You could even take things a step (or ten) further with a Link beanie hat that includes Elven ears.