Couple directions we could go....
New.. Not a LOT of choices there, and NONE of them are cheap. Covington (Cole) makes a planter still. (Sweet Farm Equipment carries them) Also, Yetter Corp. still manufactures what WAS the Deere #71 flex-planter row units. With a 2-row toolbar hitch, you'd be looking at better than $2000. A top quality planter though. It wasn't all that long ago that the Deere #71 was used as row units on 12, 16, 24, and bigger AG planters.
Used, you might find a #71 Deere planter at a decent price yet. (There's a couple on Ebay now. Look to spend about $750 + this time of year) You can find #71 units around $150 a row in the "off season" Older Deere, Cole, Burch, Ford, IH, AC. ect 2-row units pop up for sale at auctions from time to time. You never know what you're going to find, and parts for these old-timers are getting scarce.
As you can PROBABLY tell, I'm an advocate of the Deere #71 unit planter. It's about as simple of a design as ANY planter ever built. Simple, accurate, easy to use, light enough for smaller tractors, and still available....