Finding the wholesaler or manufacturer makes sense for other kinds of merchandise (furniture, appliances, etc.) but probably does not make sense for live animals. I suspect that most wholesalers and importers are just as clueless about newt care as Petsmart is. They want to make money - they care about keeping the majority alive and reselling them quickly, not about their long-term health.
Here is something I used to have posted on my now-defunct website. Maybe this will help you understand the situation you inadvertantly got into. It isn't your fault, but neither Petstupid nor the wholesaler is going to help you.
The Pet Shop Firebelly Newt Tragedy
When you see firebelly newts in a pet store, think about where they came from. The most common firebelly newts, Cynops orientalis, are imported from China. All are wild-caught. To get here they had to travel thousands of miles, most likely with very poor conditions along the way. Stress and overcrowding during shipment help spread disease. The ones that survive this ordeal land in a pet store where they may be thrown into an overcrowded tank with poor water quality and incompatible species (frogs, waterdogs, crabs, or other newt species). To make matters worse, most pet stores know nothing about the specific needs of newts, so their care is likely to continue to be poor in every possible way. They are likely to be fed only packaged newt pellets, which many of them do not recognize as food, and so they slowly begin to starve. Since newts can last a long time between meals, and develop diseases slowly, they may continue to "look OK" for quite a while.
Then, along comes a shopper who thinks this looks like a cute pet. They take it home with only the advice of the pet shop employees. The buyer gets a sick stressed newt that hasn’t had a good meal or decent water since it left China. To make matters worse, the buyer usually gets poor advice on how to care for it. The new pet owner is surprised to find that their cute pet refuses to go in the water, and refuses to eat newt pellets. The newt is often put at an unsuitably warm temperature, because the buyer doesn’t know otherwise. Sooner or later, sickness sets in.
Is it any wonder that many (perhaps most) people who buy these newts find them dead within a few weeks or few months?
Here is what you can do to avoid becoming part of this tragedy. If you buy pet shop newts, be sure you know how to take care of them before you bring them home. Buy captive bred newts or salamanders from a breeder. Don’t expect the pet shop to tell you what you need to know. Buy some books about newts and read everything you can.
