You can get blank blotting paper at several places.
Some art stores carry it. Chemical supply stores carry it. They call it “blotting” paper and not “blotter” paper. It’s the same thing though. But you don't want the facial or oil blotting paper they sell for makeup.
But you can’t get it perforated. You need to perforate it yourself.
Look for Whatman Grade 703 Blotting Paper
Then buy a paper trimmer and get a perforating blade for it.
SWIM has done that and it makes professional looking acid style blotter paper. Be careful, people might think it's real and call the cops on you.
You may remember me as 69Ron. I was suspended years ago for selling bunk products under false pretenses. I try to sneak back from time to time under different names, but unfortunately, the moderators of the DMT-Nexus are infinitely smarter than I am.
If you see me at the waterpark, please say hello. I'll be the delusional 50 something in the American flag Speedo, oiling up his monster guns while responding to imaginary requests for selfies from invisible teenage girls.