Nothing wrong with that! I agree, make another one the same dimensions measuring with whatever is your most accurate measuring tool. Micrometer would be best, but use a caliper or whatever if that's what you have. It's not hard, but takes a few tries when you're getting started.
The triangle insert tools are alright, and pretty commonly picked up by new users. They will get you by for now, particularly if you are wanting to get into HSS grinding, which would be a good choice for your smaller lathe. The thread has a document you can print in it that has the most needed reference posts. I call it "The book of Mikey", print that to reference while grinding. Thinking of that, if your holders will take a 3/8" tool, send me a PM with your address and I'll send you one to try, just so you can get a feel for them. And get on the list to get the models, it helps to have one to reference while you grind your first.