NAPA sells high-temp silicone hose that will work just fine for that, if you'd prefer to replace the whole rusted-out pipe. Bear in mind that the stuff is absurdly expensive - something like $8, as I remember it - but it'll last darn near forever.
On my '86 GT, I've got a four-foot length of (I think) 3/4" green silicone hose running from a sawed-off piece of the original smog tube behind the cats on the stock H-pipe up to the check valve. It smoked just a little for the first day or so that I had it, but since then, it's been fine. Main reason I used it was because I got sick of fighting that damned stock metal air tube, and once you get at least 18" away from the H-pipe's connection on that metal tube, the exhaust heat is hardly an issue at all - just make sure it doesn't lay up against the cats as you run it parallel to the exhaust past the headers, and you'll be fine.
Being that you're only dealing with a portion of the tube that's way the heck up by the front-end, you could easily get away with using plain ol' heater hose, actually, because there's almost no heat transfer at all from the exhaust to that portion. Heck, the stock connections on the front-end aren't anything special, either, as they're about the same kind of rubber hose used to come off your water pump and to/from your heater core. Take a 3/4" ID section of heater hose and two hose clamps, and poke that thing on in between the two broken pieces of metal tubing, screw it down, and you're set.