Adapter: 1/8" Dremel shank to 1/4" chuck
Even if someone makes an adapter in this direction, it's a Very Bad Idea.
1/4 down to 1/8 - no problem. 1/8 up to 1/4 - big problems.
You may exceed the speed rating of the larger shank tool - small shank tools tend to spin a lot faster, and can do so because their tools are smaller. Spin a tool that's too large too fast and you can explode it by centrifugal force. Shrapnel in all directions. Messy and frequently causing injuries.
Big to small does not need to extend the tool shaft. Small to big does, and that extension is inherently unstable. You're overloading the bearings both by putting on a tool that is bigger and heavier AND by giving it more leverage - this is bad for the bearings. You can actually bend the shaft, and once bent, it will bend more and flail about, also likely causing injuries.