I have been searching for plus size womens clothing for over 2 years now, i had a good range of wholesalers where i would buy bits n pieces from however i lost everything on my computer recently so i have to start over again... I can remember a few wholesalers but i have found that the best ones have really odd web address which means they are hidden from the public....
Your best idea is to start in something like google and yahoo search engine and just randomly think of this.
maybe visit your local stores too have quietly look at the tags i found a few places this way... some have web addresses which may lead to finding a wholesaler.
Also dont limit yourself to just buying from the UK or USA.
Getting suppliers in china are almost impossible and to be honest i dont trust them.
99% of my clothing comes from USA