Has anyone booked a Huayhuash trek in person while at Huaraz?

Hello! I am planning my first visit to Peru in late August - mid September, and one of the stops is Huaraz to do a 8 day Huayhuasah guided trek. I am planning to book in person as I hear that you get a better deal that way. My question is, how many days should I dedicate to looking for a guided trek? I currently have 2 days planned before the start of the trek to find an operator / tour as well as do some shorter day hikes. I am not too worried about acclimatizing because I will be spending 5/6 days in Cusco prior to Huaraz.

My rough itinerary:

2 days Lima

4 days Puerto Maldonado / Tambopata

5/6 days Cusco

10 days Huaraz (8 days hiking Huayhuash)

Thank you for your help!