String Trimmers

Need extra trimmer line spools for Husqvarna line trimmer model 128LD but am told they are not available. Husqvarna says I must buy a complete trimmer head which I don't need. Who wants to run out of line during trimming and then stop and rewind the one and only spool. Extra spools should be available for quick change when needed. What can you do about this? Thank you.