The slave cylinder from my Esprit was too far gone for a simple rebuild (re-sleeving was necessary), so I decided to do some research and try to find a new one. It turns out the slave cylinder on the S1 Lotus Esprit is virtually the same as a Nash Metropolitan and Austin A55. Many Formula Ford racing cars use the same cylinder as well. I found one cheap on eBay and I figured it was worth the money to simply buy a new one. The mounting holes (where the two bolts secure the slave cylinder to the gearbox) are too small and require some filing. It's an easy job though (5 minutes max), and then the bolts can slide through.
The fitting came as part of a SJ Sportscars kit that also included a braided stainless steel hose. It's a worthwhile upgrade to eliminate the old red hose, which swelled in the heat and caused the clutch engagement to be inconsistent.