We do a couple of things:
1) Throw money at them, starting salary of $250,000 plus a bonus multiplier of 0.5x to 2x gets you some very good candidates.
2) Emphasize these two things: http://www.cayman.com.ky/caymans-tax-free-status and http://www.weather.gov.ky/portal/page?_pageid=4421,1&_dad=po...
3) pay for trips home, give them $10,000 for travel a year and let them book their own flights.
Also it helps if this position is a set term, ie 2 years. I find having a definitive end date makes most things bearable as it gives people certainty about when their expat trip will be over. This is especially critical if there is a spouse or family that will be coming along with the employee.
Let people know that after their 2 year stint is up they are welcome to move to your head office if there is one somewhere else.
EDIT the salary and bonus I mention, only to make the point of paying well. The type of person we typically hire is very in demand, hence the pay.