I'm looking for an AM transmitter. Yeah, AM.

Or one of these.

Did you miss this post by the OP?

If the OP can rebuild an AM radio, he can easily build in an auxiliary input and run anything he wants from any source right into the radio, and play it from the speaker.

Going back to the OP’s question, I’d be looking for a used Talking House AM transmitter. The new ones run from $125 to $175 and there are plenty of used ones out there, primarily because they’ve been replaced with FM units. It’s exactly what he needs.

Making/building an AM transmitter is actually pretty easy, as it’s a simpler type of circuit (when compared to an FM transmitter). The problem is that there’s not much demand for the parts.

You don’t need any special parts, though. If the OP rebuilds radios, he or she may already have enough spare electronic parts to build a low-power AM transmitter.