The link to what I use exactly is in that post I already quoted.
EDIT: ok, so maybe not. The site is listed as well as the product name. I get 100 yard rolls of perfectear plus medium tack. It comes in 6" wide too, which can be handy. Wrangling 12" wide tape can be cumbersome if you’re doing irregular/narrow leather bits. The 12" is indispensable when masking sheet materials though.
You’ll also need a way to apply the masking, I use a 3m spatula, works great (home depot and elsewhere)
If you can’t get the spatula in time, you can even use a credit card or even a cut rounded rectangle of plywood or something in a pinch. The spatula is perfect really, it has just the right amount of give to let you get good adhesion without putting too much pressure on the leather.