Found it from this Next Pats podcast via Phil Perry last offseason when they had a joint practice with the Eagles:
The list for those who can't/don't want to watch, these are guys they practiced against in joints (year listed is the year the practice took place) that found their way to the Patriots over the next few years:
2010
Falcons - Michael Jenkins
Saints - Ramon Humbar, Will Smith
2011 - No joint practices.
2012
Bucs - Lagarrette Blount, Aqib Talib, EJ Biggers, Dakota Watson
Saints - Travaris Cadet, Akiem Hicks, Jonathan Casillas
2013
Eagles - Damarius Johnson, and Patrick Chung (if you count him)
Bucs - Tim Wright
2014
Eagles - Bradley Fletcher
2015
Saints - Brandin Cooks
2016
Bears - Rob Housler
2017
Jags - Luke Bowengo?
Texans - Eric Lee, Riley McCarron, Ufomba Kamalu, Eddie Pleasant, Stephen Anderson,
2018 - No Joint Practices
2019
Lions - Dee Virgin
Titans - Jonnu Smith
2020 - No preseason at all
2021 (not in the video)
Giants - Jabril Peppers
Eagles - TBD
Some of the names are (to be generous) very forgettable. But there are some standouts like Blount, Talib, Hicks, Cooks, and Jonnu.