I have a confession to make: some of my citations use fake page numbers.
Why do I do this? Because sometimes there just aren't any page numbers or I cannot find the page numbers for a document with any reasonable amount of searching. This happens especially often to me with computer science papers, where some venues just don't bother. Online journals also often have unusual approaches to page numbering, sometimes giving a DOI-like token rather than a number. In other cases, such as some book chapters, there are page numbers, but the versions accessible online aren't marked with them.
My preference in these cases is simply to omit the page numbers: citations are about information accessibility, and if the page numbers aren't a meaningful part of accessing that information, then I see no point in trying to fit the citation onto that particular Procrustean bed.
Occasionally, though, a journal with a particularly zealous and inflexible copyeditor will force me to add page numbers to things that don't have page numbers, and that is when I use fake page numbers, simply numbering an N-page document as pages 1-N.
Bottom line: don't sweat the page numbers, much less the volume number.