Autonomous Transaction

My requirement is to create a cross reference for an item (not customer item cross reference) once it is entered. I am using an after insert trigger on MTL_SYSTEM_ITEMS_B to call a procedure that is defined as autonomous transaction. The procedure calls API to create the cross reference. The API errors with "Item cannot be found". How to better handle autonomous transactions ? Is there any other way to handle this better ?

Thanks

Rajitha