Jianghaihui via Amazon offers the Onhi Wireless Bluetooth Keyboard Case (Gold pictured) in several colors for $58.99. Coupon code "546DMWAY" drops it to $47.19. With free shipping, that's the lowest price we could find by $3, excluding the below mention. It will fit the iPad Pro 10.5" tablet and features a backlit Bluetooth keyboard.

Not in a hurry? It's available from Ss.well via eBay for $45.59 with free shipping, but ships from mainland China and may take up to six weeks to arrive.