SGC:
https://www.gosgc.com/population-rep...20Master%20Pop
PSA:
https://www.psacard.com/pop/t206
I know the PSA pop report you can search just by card back, so all the Broad Leaf, for example. SGC's search is at the top.
As a caveat, I just spent a few weeks taking the pop report from both sites and putting it into Excel for my purposes, and there are inconsistencies on the PSA pop report. When you search just by back, you will get different numbers than when you look by player in a few cases. There are also issues with the way PSA labeled cards and entered them into their pop report. For example, players who have both a Sovereign 150 and Sovereign 350 sometimes just got labeled as "Sovereign" in the pop report, because the 150 and 350 totals do not add up to the general "Sovereign" pop count.