Honestly, skip the battery grip. I had issues with the weight on my last trip and it's just not as good as expected for walking miles. The 90D body is already 701g and adding a grip basically makes it a brick. Unfortunately, the Slide Lite is way too thin for your setup. It's only 32mm wide and will dig into your shoulder once you add that lens weight. You need the wider version and some extra juice.

• Peak Design Slide Camera Strap 45mm - the wider padding is non-negotiable for a 1.3kg rig.
• Canon LP-E6NH Lithium-Ion Battery - the 90D eats power if you use live view or wifi.
• SanDisk 128GB Extreme PRO SDXC UHS-I V30 - your 32.5MP files are huge, dont skimp on speed. That 18-135mm is a solid all-rounder but it makes the camera front-heavy. The BlackRapid is okay but the tripod mount attachment is kinda annoying when you want to put the camera down flat. Stick with the wider strap and you'll be fine.

Saw your post and thought id chime in since ive done the Tokyo trek many times with a DSLR. 10 miles is actually a conservative estimate once you start exploring Shinjuku or the shrines... your feet will feel it more than your neck if you pack smart. With a 90D and the 18-135mm, you have a solid all-rounder, but that lens is basically a vacuum for dust when you're zooming in and out all day. Maintenance and power management are gonna be your biggest hurdles in Japan. Heres what id grab with that remaining $200:

• Spare power: Grab two Canon LP-E6NH Lithium-Ion Battery. Third-party cells can be flaky with the 90Ds power management system, so stick to OEM for peace of mind.
• Maintenance: A Giottos Rocket Air Blaster Large and a LensPen NLP-1 Lens Cleaner. You will get smudges on your glass from the crowds and humidity, and the blower is vital for the sensor.
• Organization: Look at a Tenba BYOB 9 Camera Insert. It turns any standard backpack into a padded camera bag, which is way more discreet for the subways than a dedicated photo bag.
• Charging: A Nitecore UCN2 Pro Dual Slot USB Travel Charger is a lifesaver. It runs off a power bank, so you can top off your batteries while you're eating ramen or on the Shinkansen. Japan uses 100V, so your gear will charge fine, but having that USB option keeps you mobile without hunting for wall outlets. Keeping the kit light and clean is the way to go.

Re: Honestly, skip the battery grip... Unfortunately, the 90D buffer is disappointing with slow media. Get a SanDisk Extreme Pro 128GB SDXC UHS-I 200MB/s for those 32.5MP files...