Some hooligan decided to strip my bike the other night. I replaced everything except this strange frame bolt that holds on the rear triangle of my Raleigh Technium at the top of the seat tube. The jerk only stole half the bolt, but I have no idea where to get a new one.

Anybody know a source?

Is it the same threading as the seat post bolt? If yes, does the seat post bolt fit, but it is not long enough? They do make seat post bolt in different lengths, or at least they used to.

When restoring an old bike... I look for parts at my local bicycle co-op. They don't have tons of parts... but they often have the part(s) I need.

Raleigh dealer?
Maybe take out the one that's left and measure? Look for something called a "sex bolt" . . . McMaster-Carr, etc.

Better get a couple extra when you find them; the intact bolt in the second photo looks like it has cracked. There is also "Sugino" stamped on the bolt head which might be an additional clue to finding a replacement.

AKA "Chicago Screw"

The bolt marked "Sugino" is a standard seatpost clamp bolt and almost any LBS will have them. And, yes, the missing bolt is indeed a "Chicago Screw". The OP may be able to find a suitable one at a well equipped hardware store or a Fastenal shop.

If the remaining piece is the nut then you could use an socket head bolt and a washer for now. If the remaining piece is the bolt then likely a seat post bolt nut or brake nut will work. It does look like a seat post bolt but I don't know if you will be able to find one long enough.

Wow! Thanks for the lead at McMaster. Search "sex bolt" (who woulda thought of that?) McMaster-Carr

Use the tamper-resistant kind. Or the hex key variety.

Probably had a Techinum that needed the Bolt A rivet would work too..

seat post binder bolt looks cracked. left side ..

You guys rule, thanks for all tips!