Just found this thread. Before you drop any more cash, are you planning on using mostly heavy glass like a Noctilux or just some compact f/2 primes? The balance of the M11 shifts a lot depending on what is hanging off the front. If you find the body slippery, I’d honestly skip the official Leica hand grips and look at these for your Tokyo trip:

• Oberwerth Half Case for Leica M11

Leather gives way more friction than the stock finish. It makes the camera feel more like your old M6 with vulcanite. Plus, it protects the base since you dont have a removable bottom plate anymore. Its pricey but fits your remaining budget.

• Peak Design Slide Lite Camera Strap Black

Pretty leather straps are pure hype for long days of walking. These are kinda ugly but very functional. You can switch from a neck strap to a shoulder carry in two seconds, which is a lifesaver when you are navigating crowded Tokyo trains.

• Leica BP-SCL7 Rechargeable Li-Ion Battery Black

You definitely need a second battery. Digital M life is nothing like your M6. If you are shooting all day in Shinjuku, you will hit 0% way faster than you expect. This is way more essential than a thumb grip or a soft release. Soft releases are kind of a meme... they look nice but they unscrew themselves and get lost constantly. Just spend that money on a decent SD card instead.

The slippery feel usually comes down to the different coating on the M11 compared to the vulcanite on your old M6. Technically, you are dealing with a weight distribution shift because the digital sensor and battery add specific density to the body.

• Leica Thumb Support M11 Black Aluminum is the most efficient way to gain leverage. It uses the hotshoe to create a pivot point for your thumb, which stabilizes the camera against your palm. Major downside is it blocks the Leica Visoflex 2 Electronic Viewfinder 3.7MP if you were planning on using one.
• For all-day fatigue, the Leica Handgrip M11 Black Aluminum adds depth to the front. It features a built-in Arca-Swiss dovetail and allows battery access without removal.
• Soft releases like the Match Technical Bip Soft Release Brass can help with shutter lag perception by raising the contact point, but they can snag on bag liners and potentially damage the shutter threading. Id skip that one for travel.

Adding a bit of technical caution here because everyone is jumping on ergonomics. While the feel of the body matters, you might want to consider the technical reliability of your setup for a big trip. I would suggest skipping the soft release entirely tbh. They tend to snag on camera bags and can actually put weird lateral stress on the shutter button assembly... not worth the risk for a bit of tactile feedback. Since you're shooting 60MP, your biggest bottleneck is gonna be data and sensor cleanliness. The M11 sensor is a total dust magnet compared to film since there's no shutter curtain protecting it when it's off. You really need a dedicated blower that doesnt just suck in more dust from the environment. Also, dont skimp on the SD card or you'll be waiting for the buffer to clear constantly while the processor chugs through those massive DNG files. TL;DR: Skip the soft release for better shutter reliability. Invest in high-speed storage and sensor safety to keep the camera functional for the whole trip.

• Sony TOUGH-G series SDXC UHS-II 128GB
• VisibleDust Zeeion Blower
• Leica Screen Protection Film for M11

Congrats on the M11, its a beast. You might want to be careful with heavy hand grips tho since they add bulk you dont really need. I would suggest looking at the Haoge HG-M11B Hand Grip for Leica M11 to save like 300 bucks. It gives you that extra leverage for 60MP sensor stability without breaking the bank. Soft releases can snag on bags so just be careful... anyway, enjoy the Tokyo trip!