I am aware of the Koken Z-series ratchets that check all these boxes, but they are also very expensive.
I took a chance on the Gearwrench 81220T Compact Head Teardrop ratchet.
They advertise it as being a 3/8″ drive system in a 1/4″ body (More on this later).
Here it is compared to the rest of my ratchets, they are mostly Tekton brand non-QR:
Third from the bottom is the new Gearwrench
Compared to Tekton standard 3/8″
Harbor Freight 3/8″ QR (What I did my last set of H6 spark plugs with, it took all day combined with U-joints etc)
Harbor Freight Flex head
Tekton 1/4″ low profile. It is clearly larger, but it may be the same size as the Gearwrench 1/4″ drive. Regardless, this is a very thin ratchet.
I have a few 1″ extensions I can add on to make up the distance to the spark plug, and then easily pop them off as I back out the plug. Installation will be the reverse of removal.
I’ll post a detailed DIY this weekend if it all goes to plan.