Good luck with this. Have not used it myself.

http://www.bijoos.com/ora_docs/cr_fk_to_tab.txt

rem
rem Generate Foreign Key Creation DDL for everything pointing to a table
rem
rem Input : Tablename
rem
rem Chris Brown - Bedford, NS Canada
rem
set heading off pagesize 999 feedback off verify off
spool create_fks_to_&1..sql
REM
REM
SELECT 'ALTER TABLE '||fk.table_name||' ADD ('||chr(10)||
' CONSTRAINT '||fk.constraint_name||chr(10)||
' FOREIGN KEY'||chr(10)||
' ('||fkcol1.COLUMN_NAME||
DECODE(fkcol2.COLUMN_NAME, NULL, NULL,chr(10)||' ,'||fkcol2.COLUMN_NAME)||
DECODE(fkcol3.COLUMN_NAME, NULL, NULL,chr(10)||' ,'||fkcol3.COLUMN_NAME)||
')'||chr(10)||
' REFERENCES &1'||chr(10)||
' ('||pkcol1.COLUMN_NAME||
DECODE(fkcol2.COLUMN_NAME, NULL, NULL,chr(10)||' ,'||pkcol2.COLUMN_NAME)||
DECODE(fkcol3.COLUMN_NAME, NULL, NULL,chr(10)||' ,'||pkcol3.COLUMN_NAME)||
'));'
FROM user_constraints fk --fk to remember
, user_cons_columns fkcol1 --col1 of fk to remember
, user_cons_columns fkcol2 --col2 of fk to remember
, user_cons_columns fkcol3 --col3 of fk to remember
, user_constraints pk --pk constraint of table to set free
, user_cons_columns pkcol1 --col1 of pk to remember
, user_cons_columns pkcol2 --col2 of pk to remember
, user_cons_columns pkcol3 --col3 of pk to remember
WHERE fk.constraint_type = 'R'
AND fk.r_owner = pk.owner
AND fk.r_constraint_name = pk.constraint_name
AND pk.table_name like UPPER('&1')
AND fk.owner = fkcol1.owner
AND fk.constraint_name = fkcol1.constraint_name
AND 1 = fkcol1.position
AND fk.owner = fkcol2.owner(+)
AND fk.constraint_name = fkcol2.constraint_name(+)
AND 2 = fkcol2.position(+)
AND fk.owner = fkcol3.owner(+)
AND fk.constraint_name = fkcol3.constraint_name(+)
AND 3 = fkcol3.position(+)
AND pk.owner = pkcol1.owner
AND pk.constraint_name = pkcol1.constraint_name
AND 1 = pkcol1.position
AND pk.owner = pkcol2.owner(+)
AND pk.constraint_name = pkcol2.constraint_name(+)
AND 2 = pkcol2.position(+)
AND pk.owner = pkcol3.owner(+)
AND pk.constraint_name = pkcol3.constraint_name(+)
AND 3 = pkcol3.position(+);

REM
REM
spool off
set heading on feedback on verify on
prompt * Note: This script to recreate Foreign Keys pointing
prompt * to '&1' is called 'create_fks_to_&1..sql'
prompt
prompt * Also note: This script can only handle up to three
prompt * columns in a foreign key.