Found them! Lily Turf “Royal Purple”.
If you find weeds are difficult to deal with in the monkey grass, be aware that selective herbicides like "Image" have directions on the label that they may be used on Liriope Muscani. Image would be used to control nutrass or sedge. Other products are available for other types of grassy weeds, because sedge is not a grass. It would be helpful and appropriate to know the weed before you buy the product. I am not aware of any easy organic weeding solution that is selective besides digging, but I am aware that it is a lot of back breaking work to weed or pull up monkey grass or mondo, its tiny cousin. Around here, advertisements are common for "free monkey grass-you dig!" with good reason.
Muscani is the clumping version. Spicata is the spreading version. You may get more because this first go works well for you, and perhaps get into Spicata not knowing the difference. Muscani has a wide blade of 1\4 inch or more, while Spicata has a narrow blade of 1\8" or so. In my yard there are 6 or so different varieties, and I will generalize that the thin blade versions are generally spreading or sheeting and the wide blade indicates it will likely stay put and bush out more.
The plant is exceptional for heavy shade and does not like traffic so walking stones are often used when a path is needed. They like a consistent moisture, which stones retain, but they also fair well at the base of trees where the collection point of a broad root system moisture is always present. They like a brick wall edge for the same reason. They like proper compost and leaf litter or mold is perfect. They exist in the same condition as does iron leaf also known as cast iron plant, and would be happy to grow up on a layer of composting leaf litter.
That is a cast iron plan in the back.