Welcome @irened, I also take supplements for my idiopathic small fiber peripheral neuropathy but I only have the numbness and some tingling and no pain. I posted my story in another discussion here - https://connect.mayoclinic.org/comment/310341/.

There are a lot of different supplements that have shown helpful for relieving neuropathy symptoms. There are no cures but if they help with the pain that makes for a much better quality of life. The Foundation for Peripheral Neuropathy has a list of supplements shown to help with neuropathy on the website along with other complementary and alternative treatments here - https://www.foundationforpn.org/wp-content/uploads/2020/08/Complementary-and-Alternative-Treatments-Revised-2020-final.-1.pdf

I thought I would share a link to a small pilot study on agmatine in case you haven't seen it.
-- Evidence for Dietary Agmatine Sulfate Effectiveness in Neuropathies Associated with Painful Small Fiber Neuropathy. A Pilot Open-Label Consecutive Case Series Study:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7071502/
I always wear long diabetic loose fit socks at night to help keep my feet feeling a little better.
Have you tried any other supplements or treatment to help with the cold sensation in your legs?