You could use this script I found at http://www.siusic.com/wphchen/how-to-script-out-all-the-foreign-keys-of-a-table-106.html (archive.org) . Replace tablename1 and tablename2 with the list of tables you wish to get the foreign keys for.

select  'ALTER TABLE '+object_name(a.parent_object_id)+
    ' ADD CONSTRAINT '+ a.name +
    ' FOREIGN KEY (' + c.name + ') REFERENCES ' +
    object_name(b.referenced_object_id) +
    ' (' + d.name + ')'
from    sys.foreign_keys a
        join sys.foreign_key_columns b
                  on a.object_id=b.constraint_object_id
        join sys.columns c
                  on b.parent_column_id = c.column_id
             and a.parent_object_id=c.object_id
        join sys.columns d
                  on b.referenced_column_id = d.column_id
            and a.referenced_object_id = d.object_id
where   object_name(b.referenced_object_id) in
    ('tablename1','tablename2')
order by c.name

I needed to do something similar, where I needed the same foreign keys on multiple servers, except some had already been added. So I added a "IF NOT EXISTS" check to the beginning of the creation statements:

SELECT N'
IF NOT EXISTS (SELECT * FROM sys.foreign_keys 
WHERE object_id = OBJECT_ID(''' + QUOTENAME(fk.name) + ''')
   AND parent_object_id = OBJECT_ID(''' + QUOTENAME(cs.name) + '.' + QUOTENAME(ct.name)  +''')
)
BEGIN
ALTER TABLE ' 
   + QUOTENAME(cs.name) + '.' + QUOTENAME(ct.name) 
   + ' ADD CONSTRAINT ' + QUOTENAME(fk.name) 
   + ' FOREIGN KEY (' + STUFF((SELECT ',' + QUOTENAME(c.name)
   -- get all the columns in the constraint table
    FROM sys.columns AS c 
    INNER JOIN sys.foreign_key_columns AS fkc 
    ON fkc.parent_column_id = c.column_id
    AND fkc.parent_object_id = c.[object_id]
    WHERE fkc.constraint_object_id = fk.[object_id]
    ORDER BY fkc.constraint_column_id 
    FOR XML PATH(N''), TYPE).value(N'.[1]', N'nvarchar(max)'), 1, 1, N'')
  + ') REFERENCES ' + QUOTENAME(rs.name) + '.' + QUOTENAME(rt.name)
  + '(' + STUFF((SELECT ',' + QUOTENAME(c.name)
   -- get all the referenced columns
    FROM sys.columns AS c 
    INNER JOIN sys.foreign_key_columns AS fkc 
    ON fkc.referenced_column_id = c.column_id
    AND fkc.referenced_object_id = c.[object_id]
    WHERE fkc.constraint_object_id = fk.[object_id]
    ORDER BY fkc.constraint_column_id 
    FOR XML PATH(N''), TYPE).value(N'.[1]', N'nvarchar(max)'), 1, 1, N'') + ')
    END'
FROM sys.foreign_keys AS fk
INNER JOIN sys.tables AS rt -- referenced table
  ON fk.referenced_object_id = rt.[object_id]
INNER JOIN sys.schemas AS rs 
  ON rt.[schema_id] = rs.[schema_id]
INNER JOIN sys.tables AS ct -- constraint table
  ON fk.parent_object_id = ct.[object_id]
INNER JOIN sys.schemas AS cs 
  ON ct.[schema_id] = cs.[schema_id]
WHERE rt.is_ms_shipped = 0 AND ct.is_ms_shipped = 0;

If you do not want the "IF NOT EXISTS" checks (they really shouldn't matter), just delete the top 5 lines and add "SELECT N' " right before the "BEGIN", like this:

SELECT N'BEGIN
ALTER TABLE ' 
   + QUOTENAME(cs.name) + '.' + QUOTENAME(ct.name)

-- I found the core of this query online somewhere and I've been modifying it for some time. Credit to them for putting most of it together...