I think I bought my taps for the White Lightning liners from TOTW. However, I normally buy my taps, dies, drills, etc... from MSC. I bought a complete drill bit set (fractional, wire, letter) a long time ago. I don't remember where I got the set, but I think it came from either MSC or Brownells. I can highly recommend purchasing a complete set. You will need letter drills for the White Lightning liners. I got all the standard size taps from my grandfather; he was a machinist. For all the other sizes, I bought them mostly from MSC. I usually buy taps by the set; taper, plug, bottom. If you just need one drill bit, many ACE hardware stores carry individual fractional and wire gauge drill bits. When you buy single size drill bits from MCS, you have to buy them by the dozen.
Here is a link to a relatively inexpensive set from MSC
https://www.mscdirect.com/product/details/01186709