So its 19.5v and 6.9A and a 4.5mm barrel adapter plug. You can use a third party adapter just make sure it is stated to be compatible with the above part number. This is a big and powerful adapter and I would not take a risk of using something not specifically listed as compatible.
Post back with any other questions and please accept as solution if this is the info you needed.
The Thunderbolt port is listed as having "Sleep and Charge" which sounds good but just means it will charge a phone while the laptop is in sleep mode. Power Delivery is not listed. Most Thunderbolt ports do have Power Delivery (ability to accept incoming charge to the battery) but also in most cases if the laptop can be charged by way of a USB-C type adapter that is what HP provides. Here is a 90w USB-C adapter that will work if the Thunderbolt port accepts an incoming charge. It's still fairly big, however.
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