Luggage and bags:
All kind of luggage bags are available in Pakistan. Some are a bit expensive though!
Clothing/Shoes/Weather Gear: Western clothing is available in Pakistan (no shorts in the Northern areas). Quality shoes also available in Gilgit.
Toiletries and Medical Supplies: For Stomach problems, try Hamdard's Ispaghol Or Husk as its called. Very effective. Have one table spoon every night with water in Pakistan. For stomach upsets, Polycrol is the most effective medicine. Keep Oral Rehrdating Salts (ORS) to avoid dehyrdration.
Smelly Mosquito repellars are more effective than less smelly ones. Baygon and the Mortein (choose the smelly one) are most effective. Mospel is a liquid cheaply available which repels mosquitoes.
Photo Equipment: Cameras are available for sale and rent in Gilgit/Hunza.
Camping/Beach/Outdoor Gear: Stoves, Sleeping bags are available in Gilgit. Not much choice in selection in Hunza, though.
Miscellaneous: Electronic goods, silks, perfumes of good quality are available at extra-ordinarily cheap prices at Gilgit.
Luggage and bags:
Normal luggage and bags. Be sure about the kilograms limit. They can overcharge you quite a bit for heavier stuff.
Clothing/Shoes/Weather Gear: If you go in the summer, bring normal light clothing for Hunza and nearby areas. Sweaters will be required for Khunjerab expeditions. Bring good hiking joggers. No serious weather gear required.
Toiletries and Medical Supplies: Bring something for your stomach . Many foreigners complain about stomach problems like diarherria. All major medical supplies are available in Gilgit. You can bring a mosquito repellant but local stuff is more effective and safe.
Photo Equipment: Too much light in the days can ruin photographs. Bring light filters. Batteries are normally confiscated at the airport (Don't know WHY). Buy them from the places where you intend to go.
Camping/Beach/Outdoor Gear: Bring a sleeping bag if you intend to go hiking to Naltar, Fairy Meadows. Other places have good hotels.
Miscellaneous: All major requirements are available in Hunza and Gilgit.