Flexible supplier -
I recently got in touch with Wendy Li from Shenzhen Feican Technology Co., Limited. I inquired about the Bluetooth RGB LED controller for my client. She replied a little late but she was able to answer all of my concerns in complete detail.
I recommend them for being flexible because they agreed with my payment term proposal which is 30 -40 - 30 (30% at PO, 40% when free-on-board, 30% once it clears customs). Wendy even offered to send samples first.
It would be nice to visit their factory to check the quality of their products in person but I would definitely consider their company to my supplier list because of their willingness to meet your requirements.