Bluestone Perennials lists many plants. I did not check if they carry the one you want.
Since Ajuga is so vigorous, and able to set seed, you may find that a good part of your plants are different, in a few years, from the selected form you planted. My wife brought me one burgundy plant, from a plant sale, somewhere. I limit Ajuga to selected areas, as it had plans to take over the entire planet, and have not seen a burgundy plant for 10 years, among the many generations that I tolerate or pull out.

I found 'Party Colors' locally and have it planted at the front of a border in part shade. It is doing beautifully & seems very vigorous.