there is an avatar body you can buy in the catalog you don't need an access pass(confirmed to be 18 or older) its called : nudeavi
but i cost 11633 credits
you must have gotten the transparent dress the first time. imvu staff caught it and deleted it taking it out of the inventory of all who bought it
this one i mentioned is the avatar body itself you can mask it over your regular clothes and when you take your clothes off instead of that little green shirt and shorts you are naked.
(if you really want it, it's double credit earning from Tuesday to Thursday do some of those offers) :P