Several eBay sellers sell patterns for the TOS skant (katarra8, intergalactic, etc), but all of them are the tri-swirl design (seen on Nurse Chapel, occasionally on others in velour in the 2nd season, and on all the ladies in polyester knit in the 3rd season). If you want the first season design, you'll have to fiddle with a regular pattern and adapt it. I haven't found a TOS skant pattern for that one yet. In fact, if you find one, please let me know!
Be warned that many people complain that the patterns run small (esp in the sleeves) and the skirts are very, very short. Like, crotch-skimming short. Actually, if you look at the series, the skirts really were that short (they wore Danskins dance pants underneath in matching colors), but these days that lack of length makes a lot of people nervous.
Many people online say they added a few inches to the skirt length, and some have said they needed to lengthen and/or enlarge the width of the sleeves, add gussets in the armpit area, and other mods.
I got my pattern from katarra8 on eBay. She also has an etsy shop if you don't like eBay. She also sells the patches, rank braid, and other accessories. However, I have yet to attempt to make a mockup of the skant (been too busy this summer). I've only managed to transfer the pattern so I don't have to cut up the original. I looked online at other people's experiences sewing it up, and to say they vary wildly is an understatement. It should be an interesting experiment when I get to it.
Here is the pattern I bought, if you are interested:
But as I said, there are others available on eBay and etsy. I have no idea if they are all the same pattern, or if they are produced by different people. Good luck!