Legendary Canadian caver Mike Boon passed away in 2014, but portions of that '65 - '66 Jamaican expedition are documented in his book
Down to the Sunless Sea, available online at this tribute website thanks to the Alberta Speleological Society:
http://www.caving.ab.ca/boonThe
NSS Library shows a copy of the full report on file, which you may be able to access.
Or, you may have luck contacting also-legendary karst hydrogeologist Dr. Derek Ford of McMaster University, who led(?) the expedition. The University's website lists his professor emeritus email address as `
dford at mcmaster dot ca`, though I'd recommend checking the NSS Member Manual as well.
Finally it never hurts to contact
SpeleoBooks when searching for rare books of this sort.