Here's something unique that showed up on eBay, I don't think it's worth the price, probably can be found cheaper, not that I want one. But it is interesting and has some unique features https://www.ebay.com/itm/358165842496
Bluetooth AM Transmitter Converter for Vintage & Classic Radios Rechargeable
$89
Excerpts from the description:
Bring modern Bluetooth audio toANY AM radio without modifying, rewiring, or compromising originality. Your radio remains100% original and fully reversible. Older AM radios especially benefit fromstable lithium power. ...
This is not a budget knock-up, DIY experiment, or disposable transmitter — it is engineered for stable signal, cleaner audio, and true portability. ...
Most AM transmitters sold online use disposable AA or alkaline batteries, which lose voltage quickly and degrade performance. AM Pros uses a rechargeable 9V lithium battery, providing the stable voltage AM transmission depends on. ...
Built-in 9V rechargeable lithium battery – fully portable
12V DC mains power input (5–12V DC) ..
HANDS-FREE CALLING (RARE FEATURE)
Unlike most competing AM transmitters:
✔ Supports hands-free phone calls
✔ Calls play through your AM radio speaker
✔ Ideal for home radios, workshops, and classic vehicles
Most budget AM transmitters do not offer calling support.