You can bring Stones and Jal of Parvati Sarovar and Gauri kund as souvenirs of Adi Kailash & Om Parvat Yatra.Holy water can be used during pooja at home and during religious occasion.
You can buy Adi Kailash Om Parvat Puja samagri from Dharchula because that is the last market available in the Adi Kailash & Om Parvat route. However, TTT will be providing a bag of puja samagri to each group for Havan Pujan at Kala Pani.