​Hello everyone. I have recently decided to upgrade my old touring bike. One component I want to replace is the fork - I opted for a rigid one instead of the old suspension. The problem I run into is that there are not many options on the market of the threaded rigid forks with the same steerer length (150 mm) that my old fork has. Searching both amazon and ebay returns literally zero tangible results. I am not experienced in bike mechanics, so I am wondering what options I have in general: a)to buy a fork of close dimensions (say, 175 mm of length) and use some additional components to accommodate it to the frame; OR b)to replace the threaded fork with a threadless one – there seem to be more of those available and, as I understand, the longer steerer would be less of a problem here, as it would be easier to adjust the length to the frame – right? The downside of this solution would be the need to replace the headset as well, which is not a trivial procedure per se.

I tend to choose option a), but I am not sure if it is viable at all. Is it possible to accommodate a slightly longer (threaded) steerer to the frame? If yes, which components will I have to purchase? What are the limitations which I have to take into account? Please advise. Thank you.