I put together one of those kits when I was a kid. I still have it. The half cock notch could be deepened a little. I just got a plastic bag of castings as I recall. No instructions, no nothing but a bag of castings. Fortunately, I didn't need instructions. If you know what you are doing, you can have a nice tinderlighter indistinguishable from the original. I checked out the link. It sure has gone up in price just for some bits of brass and steel. I think I bought my "kit" for $25 about 30 some years ago.
The one pictured above is a German model, I believe, all iron. I have thought about making one, but I have too many other things on my to do list.
If you can do some basic blacksmithing, it shouldn't be too hard to make. I figure it would be about a weeks work for me, but these days, the only way it is getting on the schedule if somebody paid me for it and then it would still be next year.