The downside is that rubber boots are not fantastic footwear, from a comfort, support, or grip perspective. Finding a pair that can stand up to those tasks is difficult. I have in my gardening arsenal a pair of rubber Wellingtons from Smith & Hawken ($62). I've retrofitted them with Superfeet insoles ($28) for better stability and arch support. They're well-made boots and work pretty well for extended use, although I must say I haven't trekked in the jungle with them.
It appears the place to go for really serious "Wellies" is the United Kingdom, where they originated. There, a company called Le Chameau makes Wellies with Vibram soles. The model you'd want, I think, is the Vega, which sells for about $150. The challenge will be finding a pair in the United States. But, you might visit one of the Vega's online UK dealers and see what you can work out. Try www.wellieboots.com.Happy hiking!