I’ve been doing a bit of research on this. You can buy Sirius antennas all the live long day, the plug is universal. But you’re held up by the integration module between the radio and the antenna.
It seems that any of the Chrysler vehicles with the oval radio used
the same module. You might be able to find one at a junkyard and also snag the two plugs that go between the radio and the module, then splice wires in at your preferred length. If not, the FSM shows it would be really easy to create.
Part # is Mopar 05064074AC. Here’s the link to a module on eBay. You could probably find one in a JY for cheaper tho.
https://rover.ebay.com/rover/0/0/99?loc=https://www.ebay.com/p/28023752352