It was on the car when I purchased it. At one time these were fairly easy to find in the U.S. but I just did a quick search and can't seem to find one. It might be worth checking with the larger Harley component suppliers or one of custom bike builders that previously used the X-Wedge like Big Dog Cycle or Combat Motors to see what they may have.
The three hole pattern on the throttle body is the same as some of the Harley Davidson models with the same throttle body diameter, and I see many similar air cleaners for H-D but the two mounting points on the cylinder heads for the air cleaner backing plate are wider on the X-Wedge engine. Summary: H-D filter elements and various top covers are readily available, it's the backplate that is unique to the X-Wedge. Note that the correct backplate is needed as said backplate is part of the mounting for the throttle body.
Apologies for getting you excited about something that may be unobtainable
An edit: After looking at my car, I was reminded that the air cleaner has two metal mounting ears or extenders, that fasten to what is highly likely to be a H-D spec filter assembly thereby adapting it to the X-Wedge motor. The air cleaner assembly is known as an S&S Steath air cleaner, and they separately sell decorative covers to suit your preferred style.
