A few years ago I found that many bike shops refuse to cut additional threads on a steerer, much less threads on an unthreaded steerer. The reasoning was that they believed it dulled the cutter, and most of them only used it to chase already cut threads. I did find one shop that would do it for $25/inch of threads. I thought this was a reasonable price.
So, for the OP, perhaps the best bet would be to cut the unthreaded steerer to a "well measured" final length. This would be head tube length + headset stack height, including washers. Once done, cut threads as [MENTION=362748]SquidPuppet[/MENTION] shows.
If you want to keep the current fork, that would appear to be your best bet.
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If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.