That’s going to be a tough one. The smallest case I have used is the Corsair Obsidian 250d. 2 slot mITX case but it is around twice the height of the Element Q. But it fits a full size power supply, 4 hard drives (2x 2.5”, 2x 3.5”), a full length 2 slot video card, and even room for a 240mm AIO cooler.
But I guess it depends on your application and where you plan to place it...
These aren't easy to find anymore, but this is one that I am currently using:
AZZA Z Mini (CSAZ-103)
13.5"x4.4"x17.3" (342mm x 112mm x 440mm HxWxD)
It's a bit short for your needs (almost 1" less than you were looking for), but it can support a dual slot GPU (up to 280mm), 240 AIO (can actually fit a 240 + 120 in it, but they need to be slim due to the cases < 4 1/2" height!), utilizes a full size ATX PSU. It also has room for a laptop sized optical drive as well. It's not to horrible for a 10.1L case, but it's very difficult to find, I was trying to buy a second and couldn't find one. Mostly I'm going to just listen in and see if anyone has any suggestions that are similar. I've been looking for similar style cases, but haven't had great luck so ended up getting a cube style (I've got 2 Silverstone SG13s, one black and one pink).
Found this one: https://www.sliger.com/products/cases/cl520/
8L full size GPU, no room for water, don't know if you care for that or not. They don't include everything and you have to pay extra for accessories (that's a Sliger thing with all of their cases), that said you can chose which accessories you want/need.