I have been using an Amazon Basics USB-A to USB-C with my 11” iPad Pro since I got it on launch day (slightly cheaper than the Belkin linked in the other comment): https://www.amazon.com/dp/B01GGKYS6E?ref=yo_pop_ma_swf

The link to my dongle is under "Third Party Hub". I am using a USB 3.1 cable, don't know the brand. I've had it for a little while.

I'd try this https://www.amazon.com/AmazonBasics-Type-C-Adapter-Charger-Cable/dp/B01GGKYS6E/ref=mp_s_a_1_3?keywords=usb+a+to+c+data&qid=1569786694&s=gateway&sr=8-3