Good old eBay - item 251231854765 is the same as mine (£13.50 delivered). You'll also need a couple of M6 x 25mm socket cap bolts, e.g. eBay item 120956475577 (£1.24 for 12). So the whole set-up for under £15.
The Vauxhall sunglasses holder has some metal reinforcements in the securing holes and these need to be prised out before you can fit the replacement bolts.
The flash in the photos has made the colour look quite different from the headlining but it's hardly noticable in normal lighting.