I don't think they are all that popular. The 309 was discontinued in 1979 after about 22 years of production. They were never as popular as the International or John Deere 2 row planters, and most new parts have pretty well dried up. NH does have some parts andabout 32 different plates currently listed, however. Lincoln Ag, which specializes in new plastic planter plates and has hundreds in stock (at $11 each), does notlist any for the 309. I suspect that the market is just not there.

Interestingly, agood 30 year old 2 row mounted planter, of any brand will usually bring more today than it cost originally. While a 4 or6 row planter of the same vintage and condition brings about 20%-30% of its original cost.