I found this new old stock Girling .87" Right Hand external clutch slave cylinder in a box of parts. It was purchased from Pegasus in 2018, still in original Pegasus bag.
But Wait! I found more stuff,
Girling .70 master cylinder
Girling .70 master rebuild kit
Girling .625 master rebuild kit
What appears to be a new throw out bearing
1.3" Long clutch bobbin
7 LD19 caliper seals
another slave cylinder that looks like it was left in the fridge well past its "use by date"
$130 Plus shipping.
Steve