Who can he spar with that's as unorthodox as Wilder and has equal power as a Wilder? He is the HW Maidana. You can't really prepare , you just have to adjust and survive.
I don't think he needs to find someone with Wilder-like power, it's only sparring and he doesn't want to take too much punishment no doubt. However finding a stylistically similar fighter will be very difficult indeed.
No sparring partner is gonna stop him from being a big stiff idiot. AJ's just lucky he'll be able to blame the wilder loss on getting caught with a lucky shot. The Mac would have embarrassed him and won every round like he did to Wlad. #MacYear