You could go the other way and cut the spoke heads off and use Z-bend pliers to creat your desired spoke length.
See this link —> https://jimlangley.net/wrench/espoketool.html

I actually created a replacement spoke this way for one of my bikes about a year or so ago. I didn’t have the z-bend pliers…just did it in the bench vise…but it works. It’s still on the bike working just fine. I’ve seen pics of wheels built entirely with Z-bent spoke. It looks OK, uniform, and works well. And, at $20.00 the pliers are a lot cheaper than a spoke threading tool.
https://www.amazon.com/Hangar-9-HAN1.../dp/B0006OBMJI

Dan