I never used a lot of the thumb grip accessories available for Leica cameras until I got my Leica Q. The Match Technical Thumbs Up grip for the Q has made all the difference in the world, and I can't imagine shooting without it now.
When I got my Leica Monochrom (Type 246), I wanted to get another Thumbs Up grip, but the problem was that I wouldn't be able to use the Thumbs Up and the Leica EVF-2 in the hot shoe at the same time. Since I use the EVF-2 whenever I shoot my favorite lens, the Leica f/0.95 Noctilux, it was a non-starter to consider the Match Technical Thumbs Up grip.
Thankfully there is no shortage of inventive people out there! An English gentleman has designed a different product for the Leica M bodies called the Thumbie that provides the same grip benefit, but without hogging the hot shoe. The Thumbie is also significantly cheaper than the Thumbs Up grip (around $30-40), but it isn't available at mass retailers like the competition. I found mine on eBay and it was delivered to my home in the UK two days later.
The Thumbie arrives in a silver box - although it's not a Leica silver box - but seriously, who is that snobby? Inside is the Thumbie grip, some spare adhesive strips, and instructions for installation. Nothing fancy.
Of note, the Thumbie fits a whole range of M bodies - the Monochrom uses the same version as the M240. Versions are also available for the M8, M9, film bodies, etc.