SQL & PL/SQL

So I am running the following script using a subquery to return multiple records from the MTL_SYSTEM_ITEMS table and insert them into the TAXPRODCONV, but I get the ora-01427.

ORA-01427: single-row subquery returns more than one row

INSERT INTO TAXPRODCONV
(merchantid,
busnlocn,
userprodcode1,
userprodcode2,
twiprodcode)
VALUES
('01',
'DEFAULT',
(select segment1
        from mtl_system_items
        where segment1 like 'SV%-P%'
    MINUS
    select userprodcode1
         from taxprodconv),
(  select segment1
        from mtl_system_items
        where segment1 like 'SV%-P%'
    MINUS
    select userprodcode1
         from taxprodconv),
 '90000');

Note the merchantid, busnlocn and twiprodcode are constants, only the userprodcode1 and 2 will change from the subqueries I am running. I understand the ora error, because oracle thinks I am trying to insert one row. Is there a way to do this as an standard insert statement, or am I looking at writing a cursor to accomplish this task?