So I’m reporting back with what I can find now.
Glide
https://sea2.discourse-cdn.com/flex020/user_avatar/community.glideapps.com/[user_name]/360/49_2.png
Best I can find is 360x360 images.
=IMPORTXML("https://www.instadp.com/fullsize/"&[user_name],"//a[@class='download-btn']/@href")
However this is unstable, sometimes I can import it, sometimes not.
You have to get the user ID (numerical) to get the photo, and it seems many people are using their customized user name instead. Might have to ask users to find their numerical ID from a 3rd party site, which is not ideal.