Shocks for a Lehman trike

[3bird]

I have a 98 1500 with a Lehman GTL trike conversion done in 2006. The shocks are worn out and I am trying to find new ones to put on. They are Progressive's with 1364 140/190 springs. I have not found a number on the shock but was told it was a 412-4223. I tried to contact Progressive but after several back and forth he told me that the shock is over 20 years old and they don't make them any more or any parts, and he left it at that. I contacted someone else that told me that they were 412 - 4223 and I could probably get away with just changing the springs.
I was wondering if anyone else has had any experience with this problem or what shocks I could get to replace these. The place that did the conversion went out of business last year, before the pandemic, so I can't ask him.