You can buy a samco coolant kit, not sure if they have one for the Legacy but you can get them for an Impreza and it comes with all replacement pipes, exact same size as stock ones. Blue, red or black.
I'd only go Samco Dan, really really good quality. Some of those pipes get up to very high temps, so you don't want bad quality ones or they're gonna pop
I have plans to get a kit myself when I have a spare 150 quid :lol: