Well you need an internet browser that supports looking at the html source code. On Windows I think Firefox has that, and on my ipad I have an excellent browser app, a german one called icabmobile which has a lot of spiffy functions including a "source code" function to show the html source and then an "in-page search" function. Safari doesn't support this. There is I think a google chrome Vin finder plug in (there are lots of posts on this in this forum) and I have used it but can't quite recall what it does. When you can see the html source code of the account page you just search (find) the string "rawAmount" and you may have to be careful to spell it exactly (upper and lower case) depending on the browser. This is done on the account page you get after you click on the "manage" option - for me the page that comes up as "Lecontes Tesla" with a picture of the car and the status of delivery, etc. The one where you can click on the order agreement, the final invoice, the rego papers etc.
Re leasing, I don't know if the search for payments made is for the same string or not but I would think it likely to be the same. Perhaps someone else who has searched the source code on a lease paid Tesla can comment. I would think at the very least your $350 or so order deposit would be there as rawAmount And presumably any other lease payments would be there nearby in the source code.