If you have an antique bed or a non-standard frame, these sources specialize in custom-cut orders:
: Provides custom-width bed slats for King, Queen, and Full sizes. They often include hook-and-loop fasteners or black strapping to keep boards in place.
You can buy replacement bed slats from a variety of major retailers, specialty custom shops, and home improvement stores. Depending on whether you need standard sizes or custom dimensions, the best options include: Major Retailers & Home Improvement