Just looked - you can get them on Amazon
https://www.amazon.com/dp/B00ER6DBFY/ref=twister_B00MNKCHXI?th=1&psc=1
It doesn't say it in description for the women's, but it is the RU4 that I wear (and the image of these is identical to mine and the image of the men's that does say RU4). I've never worn the RU5s. And I've also only worn the ankle socks, even in the dead of winter here; my tights go down all the way to my ankles (and then some!) so I've never felt the need for higher socks.
Thanks. I'll give them a look since I'm obviously not going anywhere today.