I know where you're coming from, I usually like to make sure I buy the right parts myself but sometimes a bit of tube is just a bit of tube!
I remember trying to replace a vacuum hose on an old Ford, genuine part was no longer available but would have been over £90 if was - even the parts guy was horrified! Ended up buying a metre of hose from eBay and used half of it, total cost about £2!! ?