Where to buy LONG top post battery to starter cables?

[JellyBeanDriver]

1986 C30 crew cab, dually, 454 engine, dual battery setup but 2nd battery not installed.

Whoever did work on this in the past swapped the cables and battery over to a top post configuration. Problem is the positive cable is running under the right motor mount and is tight from end to end - no slack. Eventually this is going to wear through and short.

Want to replace the cable with a longer one but don't know who sells them, preferably online. Don't know the length at the moment as I need to measure it (unless someone out there already knows?)

Eventually need to figure out what alternator is in there too - it's not the stock one, might be a C130 but the output at idle is lousy.

TIA,
Dave