I brought back 5 litres of 70% alcohol white rum from St Lucia a few years ago (no brand name just local stuff) and used it with much enjoyment in many cocktails.
I was initially searching for Bacardi 151 because it was the only rum I could find online that was a similar strength. However, it's cost and Andy's warnings lead me to believe that the 63% Wray & Nephew white rum available in the UK may be a better bet.
This rum is not for inclusion in Tropicoma as that, I believe, is made to a thousand year old recipe which was originally created by fat albino monks.
It will be going in one of my own punches and rest assured that any punch will be fully tested by myself prior to release and any bottles containing high strength alcohol will be properly identified as such. The original idea of using St Lucian white rum allows one to vary the alcohol content of the punch without altering the taste, it's not simply a question of including bottles of the stuff in an attempt to render drinkers unconcious. I'm far too sensible for that and anyway, last time I got someone overly pissed on overproof rum it took me weeks to clean the lumps of sick out of my wicker furniture.