I would call that a true needle in a haystack. I bought a set of Three Barrel Gun co barrels and actually managed to track down a bare receiver/ buttstock I saw sold two years prior and still didn't find a useable combination.
Finding an orphan to match and of the same grade I would consider an impossibility. The only option l would think is to buy a whole vent rib gun of any grade ( most likely 4) and fit the 32s as a second barrel set or sell to someone that has one and plans to fit it to theirs.
What are they worth? I saw 32 inch LC Smith barrels sell for over 1K. I've bought great barrel sets for $250. I never seen a vent rib Ithaca set for sale. Only takes two guys that want them x bad to sell high.
$500 shouldn't be out of the question , but in my opinion to outright state more might be optimistic. If I had a gun to mate them to I might pay more.