You can buy a 16” long shank Irwin Speedbore Spade bit for $8 and cut it up for rods..
I think the one for my plane was a 1/2” bit. Each diameter bit has a slightly different día. Shaft So I just picked one that fit.
The are not chromed, so they actually slip less than the factory ones, but aren’t as sloppy in the holes as the factory ones.
Buy two Bits and you can have really long rods.
Best to take the plane to your local box store to make sure you get the right size.