I would definitely check out: http://www.hotelcasamariposa.net/chirripo.html
for accurate information it seems it is the only trusted site you can see on the web. It is incredible. All of these false information sites like chirripo.com are just charging ridiculous amounts of money to hike up Chirripo. I recommend to search up: https://www.costaricarios.com/adventure-travel-in-costa-rica-chirripo.html
I went a couple of weeks ago and it is the easiest way to get reservations.