Travel aggregators like Expedia, Hotels.com, etc. do not give breakup of taxes (mainly HST). How to find correct ITC?

Hi PK30

This is a common problem for invoices from Travel aggregators as you mention.  The easiest solution is to take the subtotal of the individual taxable items - airfare, hotel stays, etc and multiply by the appropriate HST percentage.  It won't be 'perfect' but it'll be 'close enough' for your purposes.  If you enter notes to that effect any potential audit will come out in your favour.