Nice to meet you, I would not have expected a farmer coming from Sri Lanka.
What kinds of lights can you acquire out there? Some sort of fluorescent lighting as the others are talking about here. CelticEBE has given you some advice, definitely go look at what he's been doing with his plants, I bet you could do something similar. All you have to do is provide enough light to interrupt the full dark period. Some folks do it all at once, say 4 hours in the morning before dawn, or in the evening starting just before sunset. I have found you can stop flowering and trigger vegetative growth using a completely different method of interrupting the dark portion of the photoperiod, but it's complicated and doing it the other way is much, much simpler.
I was just talking to my own son about his problem this weekend, too, and he's in southern California and so experiences much greater swings in daylight, and he cannot have the lights on for 4 hours at a time during darkness, so my suggestion was to do it at the beginning and end of each day, 2 hours in the morning and 2 at night.
The number of bulbs per plant might be as much a function of the size of the plant as the wattage of the bulb, but to my understanding it actually doesn't take all that much to stop flowering.
The other option is to grow a tropical sativa variety that will only flower after it's taken a certain period of time in vegetative growth. I cannot offer you any advice on varieties/strains, but am posting here because I've been very curious about the issue in another tropical/equatorial location and would like to know that answer as well.