They are a US company but they will ship internationally. Tee Shirts Many shops sell tee shirts. The best we know you can get come from Next Stop South Pole and International Antarctic Centre. Try them first. Sea World usually have a good stock, but they do all have Sea World logos plastered all over them.
Many zoos sell penguin tee shirts.
Otherwise the only shorts we have seen are available from the International Antarctic Centre. The rookery print leggings available from the International Antarctic Centre are so good they deserve a special mention. Socks Penguin socks become popular around Christmas. Try Sock Shop, or any department store. As usual Next Stop South Pole and International Antarctic Centre have good supplies.