I have both the newer and the old paper 1:50,000 topos of Orizaba. I have been meaning to scan the corner with Orizaba for some time now. When I do I can post it.
If you do find a paper original for sale, grab it and hang on to it. When I was in Mexico in January I stopped at the government map store at the airport. They don't sell paper topos anymore, just digital.
In the past I have bought them from Omni. If you try them, could you please let us know if you were successful? The latest time I tried a few different sources for Mexico maps I wasn't successful. Some websites will show they have them, but then not have stock.