Most of the parts are still available for the updated shifter at St Paul. I think the only piece not available is the adjustable link, but you can buy an aftermarket one.
The original boomerang shifter is not available any more, but the shifter arm is, as it’s just a Sportster part. A little looking should find someone willing to sell a boomerang as no one really liked them.
You can also buy aftermarket Banke style ones from mcmotoworx (recommended), twin motorcycles (recommended) or engineered velocity.