That's a Chevrolet part, discontinued since 2001. It was used on many P-30/32 so it shouldn't be that hard to get. Someone is bound to make a substitute. Failing that, RV salvage yards probably have a bunch of them.
2004 National Dolphin LX 6320, W-22, 8.1, Allison 1000, Front/rear "Trac" Bars & Anti-sway Bars, Sumo Springs, Roadmaster Reflex Steering Stabilizer, 2005 PT Cruiser Toad