I have abandoned most of my commercially made kits in favor of a big zip-lock bag filled with smaller zip-locks for organization. Next step might be to contact local hospitals, ambulance services or clinics for donations of sterile packaged supplies. Some supplies still have expiration stamps, meaningless in the case of packaged dry goods: loss of sterility is event-related, not time related: take any outdates that they cull from their supplies. Alternatively you might get donations cuz places like that support mission work and enjoy the publicity. Create a list of the items that you seek, collect the donations, and fabricate zip lock kits that mirror your existing kit. Lots more labor intensive than your current practice, but perhaps less costly. Schools and churches might donate, too.