DBX made a rackmount de-esser called the 263. There are two versions, the older 263X and the newer 263A. They sell for around $50 or so on eBay. I bought a pair for $100, for example. DBX also made a more famous de-esser called the 902, but that requires their 900 series lunchbox.
There are a few Orban models, as has been mentioned. There's also a de-esser made by BSS I believe. That's not all of them, I'm sure there are more.