I’ve just had a query about sourcing 670nm LED strip.
I have found it hard to get 670nm of late, so in recent Eliza-making, I’ve resorted to any old red LED strip. The main thing is to look for the one with the darkest red colour. They are available on eBay and are not at all expensive.
While 670nm is currently regarded as the bees knees, other wavelengths are also effective, including down to 630nm which is is getting towards an orange colour.
So don’t get hung up on finding exactly 670nm LED strip.
Just find the darkest red LED strip you can get, and use that.