You might be able to swing a projection morph-fit female microkini if it has breast-width morphs that remove the appearance of breats, then couple it with a futalicious projection morph?
Seems that there definately used to be one. Here's a Soto render and he says "Now, my favorite piece skimpwear has to be the M4 mankini. It was fun as it was cheap, I even did a custom morph for the Freak 4 to put it on poor Vincent."
Closest I can find for M4 is this https://www.renderosity.com/rr/mod/bcs/dz-bodthong-for-m4h4guy4/98380?AID=4987
I also have this one installed in my M4 clothes. Maybe with a transparency map it could work. https://www.renderosity.com/rr/mod/bcs/dz-singletx-for-m4h4guy4/89522