Clicky Keys and others have the right idea - - -
A type of close tight fitting compression brief of either sex (after all the fly is useless in this case) will work and perhaps allow the wearing of leggings jeggings ph tights etc. if covered with an outer
garment hiding the bulky baggy appearance of something strange and not usually found under there.
Minimum diapers to wear other close fitting garments.
Wearing taped diapers can be made real easy to wear and you don't need to tape them up. Unfold the diaper and lay it in the crotch of the brief and simply pull up the brief and tuck the excess material
away (in my case I just scissors cut the excess away before this). Now diaper changing is made easier without a total disrobe and trying to position the tape tabs.
For heavy wetters and WMD # 2 dumps this may result in a problem and too much stuff in a confined compressed area - solution more and frequent diaper changes.
This idea is not original - probably been noted mentioned several times here before.
For wearing diapers of any kind under the a for mentioned leggings gear one has to be creative to cover the underpinnings - obviously one does not go out and about in just diapers alone !