Nordost Purple Flare is a dedicated C7 (figure 8) and it's very good. Nordost Heimdall 2 is also C7 and even better, but it's a 3 core power cable from the normal range, and its ground wire is just connected at the AC connector end only.
Audioquest also do a great solid core C7, called the NRG1.5 or something like that.