Thanks for the recommendation. It is what I am looking for except that it doesn't seem to offer any upload options if there are holes in the data they retrieve. Still, a step in the right direction and I'll give it a try.
You can put data on a google drive and share a link with them. I did this for all my existing radiological data. They had no issue downloading it.
PicnicHealth CEO here. You won't have this problem because we don't miss any data :) But really, if you have old stuff we can't get anymore we can find a way for you to send it over.