Freda has made me aware that my post about USHMM and Yad VaShem is misleading.
There are many unscanned documents in the archive. https://arolsen-archives.org/en/
They have an online search site, as mentioned previously, but their collection is much larger than what can be found online at present.
And this is how you can sent inquiries:https://arolsen-archives.org/en/search-explore/inquiries/