Seems like a man of your talents could easily make one from an old front fork and something for a pointer. But I see 'em on ebay for like $100. Hmmm, take it out of the box and use it or spend 3 days on design and fabrication???
if for you it is fun, you work yourself. then it will take many days to hope you make the wheel excellent. sometimes there is a good one to do the wheel for you excellent instead. a man is to know his limits.
I built my own .... it works adequately. But if I added up all the hours I spent compensating for it's less than perfect design I could have bought a couple of them.
If I had it to do over ... I'd buy one.