2000 NISSAN XTERRA User Comment / Complaint

My car stalled at high speed (60 mph) on an interstate. i was able to start it and take to dealership where they diagnosed issue as bad speedometer controller. dashboard failure sent message to transmission that car wasn't running, causing a stall. very unsafe!!! the dealership ordered the part on 8/10 and told me the car would be ready for pickup on 8/13. at that time i had some maintenance work done as well, after being informed my car would be ready on 8/13. on 8/13 i was informed that the dealership had done the other work on my car (120k maint, battery, and fixed knock sensor) but the speedometer controller was on backorder. it has been over a month. i tried driving the vehicle but again three times experienced a stall, all while driving on interstate so consider the car not drivable and was lucky to not have been hit. i reported the delay in getting the part to nissan consumer affairs, and they are unconcerned. they told me parts only need to be made available during warranty. who these days w/ price of cars can afford new car w/i 3 years? car is only 7 yrs old and for all i know, later models could be using same part. i suspect part is unavailable because others have experienced this same issue, which is a very unsafe stall, normally at high speed. dealership even told me not to drive car. can you do anything to nissan to get part in so i have transportation to and from my job?