If you don’t need the popup, have a look at the YAKME field (no longer under development). I’m not sure, but there is also the WYSIWYG field…
Apart from that, you can, of course, always use pages instead of structure entries… maybe not ideal for the use case, but possible.
Also, @svnt is currently developing a textarea field without buttons but with right click formatting options which might work in a structure field, don’t know if it’s ready or if he wants to share it…