Go and by some proper metal fuel pipe and a bender ( no I'm not one).
You'll be wanting 5/16th (8mm) bore pipe.
Also get a flaring tool so you can flare the ends - a verey good idea on the presure side of things.
Braided hoses - are very very very expensive - especially when you also need to get the JIC (or whatever) fittings you use. - There is no point having braided hoses and jubliee fittings - IMO. If you only NEED jubliee fittings then get normal pipe.
You are right - steel will corrode (unless stainless), cast iron will be too heavy (and also corrode) and bamboo may suffer from water damage.
The 'proper' stuff is made from a copper/zinc (IIRC), or some other similar alloy which allows easy bending/shaping of pipe, will not corrode, and will withstand very high pressure.
I bought 25 foot of good quality 5/16th (8mm - the size you want) seamless fuel/brake pipe for just over £20 from my local independant motor accessory/factors shop.
Suggest you hunt out your local one, or a good motorfactors and you should be able to get some no probs. Or if you're a lazy @rse call Think Automotive and they will mail order you some (they keep a huge range in stock).
Then get yourself a pipe bender for about £10ish - or borrow one.
Alternatively you can take yours off and go to a GOOD garage and they will make a new one up.
And remember - flare the ends a little on the high pressure pipes so you don't worry about the hoses blowing off.