Can the original tires still be purchansed? if so, where?

I need to replace the rubber tubing for the rear cockpit return cable. does the rear left inspection plate under the horizontal stabilizer get to that cable?
can an ordinary bungee cord available at backpacking supply stores be used as a replacement for the tubing? Any how to advice would help this newbie.
will airing the air tanks thru the exernal fill port automatically fill the emergency tank?
Is the source to increase the pressure pumped into the tank be increased (mine only goes to 400 now, down from 500 originally) by some adjustment to the relief valve on the engine side of the firewall?
Plane was new in 96, always stored inside and 120 hrs tt. do i need to replace the fuel lines? Any and all help will be appreciated.
bf