If you can't find one, the 15 blade fan will work just fine, it just makes a bit more noise. 19 blade fans are hard to find, searched on ebay and found only one result. You could also try aliexpress.
You can't pry off the IHS on cpu like you did with GPU, it's glued to it with silicone glue. You need to cut the glue first. Watch some youtube videos on delid first before you try it. Not a difficult job if you have the right tool.
That's some good temperature, try to play some demanding games and see if it overheats.