You can use the volume GUID like this:
\\?\Volume{2a0b16cf-f76a-11df-9310-806e6f6e6963}\path\file.ext
Note that only the Unicode file functions will accept this sort of path, and the syntax has to be strictly correct. For example, you can't use forward slashes instead of backslashes.
I'm not sure how best to enumerate the volume GUIDs. One method is QueryDosDevice
but I expect there are better ways.