I think you can only get NU Skin products through NU Skin themselves - by becoming a member there you can avail of their products at wholesale. I got my membership way back in 2003 and I still enjoy the opportunity to buy their products at wholesale prices, even if its just for personal use.
TradeKey is not a very safe site to deal with. Although I haven't had any personal experience using the suppliers on TradeKey, but I have read a number of ugly reviews about them.
Here are some simple things you can do to protect yourself when dealing with any supplier found outside of SaleHoo.
1. Run a whois check on the supplier's website to verify when it was created (it is safest to deal with suppliers who have been online at least a year), who owns the domain, and where the domain was registered (the country should match the contact details on the supplier's website). We recommend using Link hidden: Login to view (replace salehoo.com with the url of the supplier).
2. Search the SaleHoo forum for the supplier's website/company name and see what other members have to say.
3. Call the supplier's telephone numbers to ensure they are genuine.
4. Purchase a sample before bulk ordering to ensure that the item meets your expectations.
5. Watch out for sellers asking you to "safeguard" your purchase by sending your money transfer in the name of a friend or loved one, or by establishing a "test question". These actions will not protect you from a fraudulent seller.
6. Low prices do not necessarily mean fraud, but radically low prices should warrant a closer look. If a price seems to good to be true, it probably is. Ask the seller as many questions about the item's authenticity as you can before you go any further.
7. Always use a credit card or Paypal to purchase goods. These forms of payment are safe because they give you a comeback if something goes wrong. With these payment methods, you can usually have the transaction reversed fairly easily if necessary.
Hope that helps. :)