SQL & PL/SQL :: Select First Unlock Record In Table For Update

I'm looking for a solution to select the first row that is not currently locked in a table and insert a record to another table that reference that first row. this is my scenario:

create table ticket
(
id number(10) not null,,
ticket_type number(1) not null,,
is_sold number(1) not null,
CONSTRAINT ticket_pk PRIMARY KEY (id)
);

[Code]...

id ticket_type is_sold
------------ -------------------- -----
10000004 1 1
10000005 2 1
10000006 1 0
10000007 1 0
10000008 2 0
10000009 2 0

SQL> select * from customer_ticket;

cust_id cust_name ticket_id
------------ -------------------- ----------
1 John 10000004
2 Sara 10000005

my goal is finding the first free ticket ( not sold ) in the ticket table and insert buyer information of that ticket in customer_ticket table. at last I will mark that ticket as a sold one in ticket table with update.

Problem is that the first transaction locks the the first row in ticket table and the second transaction running the same query goes to wait untill the first transaction commit or rollback. However when first transaction finish successfully, second transaction select duplicate id from ticket table that was selected by the first transaction!

I tried to solve problem with "skip locked" and "nowait" options with select for update, but they didn't work.