I would think just creating a new subscriber to the existing publication is better.
That is, if the articles being published are what you want on the 3rd subscriber.
If it is not necessary to keep the 3rd subscriber synchronized then you could also run a SSIS package one or more times a day to update it.
For better, quicker answers on T-SQL questions, read Jeff Moden's suggestions.
"Million-to-one chances crop up nine times out of ten." ― Terry Pratchett, Mort