I don't readily see anything in the sys schema objects, other than the DM_EXEC_SQL_TEXT function that requires a plan handle, but the procedures I'm trying to get their query texts from aren't currently running. (Maybe there's a way through their cached plans?...though the ones I'm looking for might not have a cached plan.)
Are the query texts of stored procedures stored anywhere that's queryable?
I see sp_helptext might be an option: https://docs.microsoft.com/en-us/sql/relational-databases/stored-procedures/view-the-definition-of-a-stored-procedure?view=sql-server-ver15#TsqlProcedure