String Swing is another who put a lot of time into testing their stands with nitro finishes. They can be on the expensive side.I was curious about my Hercules stand (I don't currently have any nitro finished instruments), so I looked it up: FAQs - Hercules Stands USA
It's not a guarantee, but it seems like they did some solid testing and didn't find any problems with their foam.
https://www.stringswing.com/nitrocellulose-statement/