Spare Parts Joque Harness would be the one you want. First, it fits almost all people, male or female. Size A fits hips from 20 inches to 50 inches, and size b fits hips from 35 to 65 inches. You can adjust its Velcro belt just once, as high or as low on your hips as you wish, and then you just step into it the next time like underwear. It's as comfortable as underwear as well, so if you want to pack all day go ahead.

The leg straps on each side adjust with plastic buckles. The stay firm, but move with you. It's all spandex and polyester, waterproof and even machine washable, but don't throw it in the dryer; dry it by air, it'll last longer. I hand wash mine in the shower with antibacterial soap. Since it is waterproof, you can wear it in the pool, shower, jacuzzi, etc. I do find my all black one bleeds color, and in hot sweaty sessions I was left with black marks on my pubis and waist.

It's a totally vegan product, and it has a cool labrys on the front of the belt; as well as in its little drawstring travel case. You gotta take this number on vacation with you. It's pretty inconspicuously package.

Another really awesome thing is it looks like a jock strap. There is a pocket that you can slide the dildo through. There is a built in stretchy O ring that can accommodate dildos up to two inches in diameter. You can slide double dildos like the Feeldoe, Tango, Nexus, and Share. I found that running my Feeldoe through made it have less insertable length, and my partner is a larger woman, so it was not ideal. It did, however, work better for us with a regular dildo.
The pocket can also conveniently hold a bullet vibrator as well.

Its a very sturdily built harness, the O ring is located in the clit area for maximum pleasure. I found that there was no slippage in during shower sex, or bed sex in any position.

There is a nice demo on You tube on how to adjust Spareparts.

I enjoyed the Spare Parts more than my partner did, who prefers my leather Jaguar. I also wound up taking the Joque off, and just wearing the Feeldoe held in by my muscles; because the front pocket is a little on the thick side and does take up some room. I think if I had a much longer cock, this would have been no problem. I found it perfect for driving in the back door, even with a Feeldoe. I find the Spare Parts Joque very comfortable, although a little bit too warm in the pubic area, and because it is thick spandex and polyester, it does not breathe well. We don't have air con, so it gets wet, and stays wet.

I found that this is comfy enough to use under clothes, to pack with, and the back flap allows the driver to wear an internal dildo while still putting a dildo through the front O ring. It's a very useful harness. I adjusted it once and never had to re-adjust it again... that's pretty cool!