Bicycle Mechanics - Weird cam seat post

Hello,
I recently was given an old but serviceable Schwinn 434 aluminum-frame bike that had one problem: Its seat post was splitting. Replacing it has proven to be a bit of a problem and I wonder if anyone can point me to a replacement or another solution. The problem is that this frame does not have the usual seat post clamp. Instead it came with a seat post that has a cam method of clamping it in place much like the mechanism used with handlebar stems. On the seat post, an allen wrench type socket is on the side. When turned, it pulls on a sliding cam at the bottom of the seat post just like the sliding cam used universally to secure stems in the headset.
First -- does anyone know of a source for a similar seat post? I have scoured the net and been to my local Schwinn dealer, who told me Schwinn has not made anything like that for a while.
Second -- can a seat post clamp be used to make a regular seat post work without a clamp built into the frame?
Third -- any other ideas?
Thanks for any help,
Terry Galvin

I don't believe that this type of seatpost is manufactured anymore and your options are pretty limited. You could try to find a simimilar frame with seatpost at a thrift store (very hit or miss), you could monitor ebay waiting for a similar seatpost to become available, you could ask around at some older LBSs and/or Harris Cyclery to see if they have a seatpost laying around.

I presume you could have the frame modified to cut a compression slit on the back of the seat tube. But you would then have to find an external clamp the right size for the tube diameter.

I'm not familiar with that type of seat post, but Loose Screws / The Third Hand seems to have oodles of obscure parts. You might want to give them a try: http://www.thethirdhand.com/