The colourful stipes of the 13th Doctor Who, played by Jodie Whittaker. A retro style of diagonal stripes leading to the Tardis.
Where to buy online
CloudCity7 (UK)
Amazon (UK)
TeePublic (US and UK)
NeatoShop (US)
Society6 (US)
You can find the design on t-shirts in most stores, but also on other products depending on the store (e.g. hoodies, mugs, stickers, notebooks, phone cases, greeting cards, cushions, socks etc).