Your location doesn't help you. Based on resale locations WI wasn't exactly a hotbed of Crossfire SRT-6 deliveries when new. Most SRT-6 for sale tend to be in coastal states, not as many available in the mid-west. A few options for you:

• Look at Carmax to see if they have any SRT-6s available. For a fee they will transfer a vehicle to the location closest to you with no other commitment to purchase. If you're against traveling, this is a good option. That said the SRT-6 is rare enough that Carmax won't have a wide selection of SRT-6s.
• Consider flying to buy a vehicle. You have to be very careful but you likely will be able to find a good deal with the mileage you are looking for.

Either way, good luck. The Challenger SRT8 is a totally different vehicle.