Which thumb grips are most comfortable for Leica M cameras?

^ This. Also, unfortunately most premium grips are not as good as expected for the price.

• 7artisans Brass Thumb Grip for Leica M Its solid brass and saves you $200. Good luck!

Listen, ive been shooting M cameras for a decade and unfortunately, the official Leica Thumb Support M10 Black 20015 is just not worth the 250 bucks. I bought it once and felt like a sucker. It doesnt feel any more secure than the alternatives and that logo tax is real. Its honestly disappointing how much they upcharge for a simple piece of machined metal.

• The Match Technical Thumbs Up EP-MX Black Brass is the only one I actually recommend if you want it to feel premium. Its solid brass, so it wears down nicely over time just like your M10 black chrome will. Its usually around $130 which fits your budget perfectly. The ergonomics on this one are superior because the curve fits the natural resting position of your thumb way better than the flat official one.
• If you really want to save money, the Haoge THB-M10B Thumb Grip for Leica M10 is fine, but the fitment can be hit or miss. I had issues with one being way too tight. If you're paranoid about scratches, just put a tiny sliver of electrical tape on the part that slides into the hot shoe. It fixes the wiggle and protects the finish. Its pretty frustrating that we have to spend this much just to make a five-thousand-dollar camera comfortable to hold without cramping, but that's the Leica life... Go with the Match Technical and dont look back.

I saw those Haoge ones too, but the finish is usually inconsistent and i wouldnt trust my hot shoe with them. If you want something reliable, the Lensmate Leica M10 Folding Thumb Grip is around $100. It includes a tiny rubber bumper so it doesnt rub the paint raw. Its honestly disappointing how much these things cost for what they are, but this one is solid.

Honestly, my biggest worry with these accessories isnt the comfort, its the tolerances. I've tried many over the years and seen cheap ones that are slightly too wide and actually warp the leaf springs inside the hot shoe. If it doesnt slide in smooth with zero wiggle, dont force it. Youre risking a massive repair bill just to save a few bucks. Be super careful with anything lacking a rubber gasket... its just not worth the stress.