I have the Shocker 127H horn kit. I am installing it in my son Scion TC and I ran the nylon tube from the front bumper to the rear compartment only to find it was a foot too short. So my question is what can I do to extend the line to reach. The exact part would be helpful…lol. Can you use the same hoses mounted on air compressors like the ones in Lowes ?? What are my options ? I don’t want to run a new longer line. 
and I cant get the hose to stay connected. Do you just slip it ito the nut then onto the fitting because it is tighter than a clams oven to get on
Not sure I understand your issue… is it:
a) you can’t get the hose to stay on (i.e. it’s blowing or slipping off) ; or
b) you can’t get the collet nut over the hose and then threaded to the body of the brass stem because it’s too tight?
The pipe goes on the pipe, then you push the pipe onto the tank and then do up the nut. It should then squeeze & seal the pipe on, but the pipe must sweep nicely round and onto the tank.
As for extending it, could you not just mount the Shocker manifold on the end of the pipe and take the smaller pipe from the manifold to the Shockers?
Or get two 1/2" push fit fittings and a 1/2" coupler and get HB to send you a metre of 1/2" pipe, to extend it on that way?