I've been trying to remember the name of these adjustable dumbells they have at the York Barbell store I go to sometimes. I found them here:
http://www.personaltrainingfitness.com/dumbells.html
They look weird but when I tried them in the store they actually feel pretty cool because of the balance. Plus they can go up to 130 lbs. And there's the bowflex ones (or Nautilis). They are called Select-Tech.
They work by pins instead of knobs but I think they're worth checking out. Plus then you can tell me whether they are any good or not before I buy any!
Edit* I didn't really look at the price. They are not cheap, lol. But your set of solid dumbbells will not be cheap either...
Here are some other:
http://www.quickdumbells.com/store/c...home.php?cat=1
http://www.quickdumbells.com/store/c...s.php?pageid=5 (that's the faq on those)
Another brand I've seen is called Versa-Bell. Maybe available at Wal-Mart
http://www.walmart.com/catalog/produ...e=cii_13736960
There's a whole buncha shit to be found of e-bay. I've never personally bought anything that way.