I don’t have an Anthem but would definitely get a bushing in there. Can’t think why you wouldn’t.
Is it newish? Could you go back to the dealer to find out why it hasn’t and possibly get one sorted under warranty?
If you can’t wangle one, buy one. You’ll need a new mount because the bushing will decresase the effective internal diameter. As z1ppy says, TF Tuned throw in a bushing with a mount, the others may do the same. Loco on here is very helpful but I don’t think he does mount kits yet. Loco?
You’ll need a tool to insert the bushing, I’ve just bought one of these which is a bit cheaper than the ones the well know places sell. Don’t know how well it works yet though, maybe someone else has experience.