Agreed, Co2 airline tubing is much more rigid than the normal cheap airline for air pumps and airstones. A bit more expensive for Co2 tubing but better quaility imho anyway.
https://www.aquaessentials.co.uk/ne...94_252&zenid=e316b3f7da70471dedad43ddb76e398b
Also you can get packs of elbows, T junctions, straight collars connectors which should help in setting up the air line exactly the way you would like.
http://www.ebay.co.uk/itm/Aquarium-...hash=item280368d305:m:miuAw9JYfsLvw6Xk8KrLd4w
And may be useful for you to have a valve to control how much air / bubbles you want to come out the airstones -
http://www.ebay.co.uk/itm/Aquarium-...hash=item4d44ffad13:m:mxpo0aNBCBaeASnjwHGCYSA
There are all sorts of prices and accessories online for aquarium airline stuff so worth serching around for exactly what you want on your budget as these links are just examples of what is available and to give you ideas.
Oh, forgot to mention, a tip, with co2 tubing being much tougher, you may find it hard to connect the tube to the connections of airstone or pump as its a very tight fit.
Simply putting the end of tube into hot water for a minute or two helps to loosen and make the co2 tube much more flexible thus making it much easier to push the tube onto whichever connections.