[TheApocalyptican]

If they are just lines like are used to connect the front heater core, you should be able to find them at a local parts store. Most of the local places here call them heater hoses, not heater lines....just an fyi. My only concern would be finding one who has enough length of it in stock.

If they are some type of hard line(I personally don't know what the stock rear heater lines look like, as my Sub has an aftermarket rear heat)then hopefully someone else can help.