2007 Bobcat zhs 435 swing break relief valve assy. P/N 6678788

I've got a leaky rotator brake relief valve assembly on my 2007 Bobcat ZHS 435 that's rusted through. The part number is 6678788. It still functions but leaks constantly when under pressure. I'm looking for a replacement or an alternate part number if anyone knows of one. This machine has been really solid and reliable for me, especially considering the rough conditions it works in—sand, salt, volcanic ash, tephra, sulfur and rain. That corrosive environment is what got to this component, which is why keeping it covered or inside is so important. If anyone has any information on this, I'd appreciate hearing about it.