I bought most of my hoses from Lockwood aviation. I had a few fuel lines that were marked with the Logo from a local auto parts, and some with Gates so I replaced them with the same shoes. One thing I will say is Rotax can not mandate regulations on how to maintain the aircraft. The FAA regulations are the driving regulations. According to most A&Ps, the regulations recommend inspection of the rubber hoses and it's up to the A&P if the hoses need to be replaced. In the LSRM training, I was told that I must follow the recommendation of the Manufacturer in the Aircraft maintenance manual, and Rainbow Aviation told us that we must follow the recommendation of the engine manufacturers.
Having worked with my father in the industrial rubber products business selling Raybestos hydraulic hose, Dayton hydraulic hose, I more than one replaced brittle hydraulic hose on Southern Pacific rail cars. For me it's not about the money, it's about safety. Luckily, I have no issues with not having the money available, and for $200 to $300, I don't have an issue with replacing, it's cheaper than having a fuel line break or an oil line brake in flight. I must admit some of the hoses specified an supplied by Lockwood are some of the cheapest crap hose you can buy, especially the water hoses. I personally would prefer to be able to buy a good quality radiator hoses.