Control module problem

I have a 2016 rebel ,it’s at the dealer.they tell me the control module is bad . The left rear air bag would sag after the truck sat overnight. Then I got message that read suspension not available do to payload ,after that the front end drop into entry exit mode. They said the module was bad .I have been waiting on the part for a month. I can’t even locate a used or after market replacement . I believe it may be time to replace the air suspension with a mechanical system. Does any one have any suggestions on a top of the line mechanical replacement?