Yes, Ridex, JP and a few other companies do them for about £10 but personally the complete unit by Febi at £25 is a better idea. If you search the the complete unit VW part number 038 903 315 AE you will get plenty of choices. Failure of the tensioner is often due to the alternator one way clutch failing so the tensioner dances around and makes a nasty rattle when the steering is on lock.
T50? The one I did the other day was an M10 XZN but I am at home so I can’t check. We have a kit with all sorts in but the other day I just used the VAG outer key and an M10 XZN but Laser tools list a T50 for Bosch and this for Bosch VAG https://www.lasertools.co.uk/product/3307