I have KBC's catalogue beside me , they are on page #79.It sits right beside my Machinist's Handbook. The company supplied them as we used them often. Hex dies are considered thread chasing anyway. A cheap tap and die set go on sale at Canadian Tire are about $50 last time I noticed them. Rust will dull carbon steel quickly,so it doesn't pay to spend much money.For a lot of years I used just such a set for thread chasing, only when I bought mine they were $30. If I want to thread something however,and I don't have that size, then I will go buy a good HSS split die rather than use one of the cheap ones. It's that big a difference.
The thread chasing nuts our company bought were of better quality, they lasted longer. I wasn't the purchasing agent , but I think they bought everything form Acklands-Granger. You can try Zorro.
Machinists look down on hex dies, they are a common millwright tool, though. Here is KBC web site link
https://www.kbctools.ca/CatSearch/103/hexagon-dies KBC is a machine tool supplier.