For what it's worth, I think it's actually smart buying a test item yourself first before taking a wholesale order and openly marketing it.
Yep -- this is absolutely a necessary step for dealing with an overseas supplier, no idea why people skip it so often. If you have no idea how good the product is, how fast it ships, what the packaging/labeling looks like (if you're dropshipping) etc. then how on earth can you market any supplier or product? It's a fundamental part of serious research.
As far as the question of negotiating samples, your better bet would be to find a trade show near you and attend. There are wholesale shows all year round; most advertise pretty heavily, and many showcase a huee variety of foreign importers who otherwise are hard to find and connect with. There, you can handle the product, meet and greet with sales reps, and in all likelihood negotiate a good sample order (assuming they aren't running a sample special for the show, which is pretty common.)