There are may websites with statistics regarding EOS. Unfortunately I didn't find any regarding archival Nodes. Can you please point me to some statistics about how many archival nodes exist?
It's not possible to get all archive nodes connecting with any eosio network because eosio doesn't store any information about archival node unlike block producer nodes but you can retrieve information about nodes that are connected with your node by using net api plugin. Some platform stores nodes information and help in checking node sync status with network.