Can You Buy a Cover for the Nintendo DS GBA Slot?

No dedicated cover exists. The Slot-2 (GBA) opening is recessed and integral to the chassis—adding a cover would block cartridge insertion/ejection and interfere with the hinge.

Practical Protection

• Carrying case/sleeve: Full-device protection (hard shell or neoprene) keeps dust out of both slots.
• Screen protectors: Top & bottom—also reduce debris near slots.
• Compressed air: Occasional blow-out keeps Slot-2 clean.
• Keep a dummy cartridge (cheap GBA game) inserted when not in use—best dust plug.

No aftermarket plug is needed; the slot is durable by design.