Small island and low-lying coastal nations at greatest risk from climate change should be given at least 10 per cent of the fund, the group, headed by Britain's Queen Elizabeth, said at the end of the three-day summit.
"Climate change is the predominant global challenge ... For some of us, it is an existential threat," the leaders said in a statement.
The deal is seen as a push to gather momentum ahead of the UN climate conference to be held in Copenhagen from December 7 to 18.
"My conclusion from these consultations is very clear. We sense strong support at the highest level to reach an ambitious deal in Copenhagen"
Lars Lokke Rasmussen,
Danish prime minister
The summit was joined by Ban Ki-moon, the UN secretary-general, Nicolas Sarkozy, France's president, and Lars Lokke Rasmussen, the Danish prime minister.
"I will leave Trinidad fully convinced that it will be possible to reach an ambitious agreement in Copenhagen,'' Rasmussen said after the group's statement was released.
The meetings were closed to the media, but after the talks Ban was positive about its consequences.
"My message to all the world leaders here today has been simple," said Ban.
"Stay focused, stay committed and come to Copenhagen and seal the deal. A deal that is ambitious, a deal that is equitable, a deal that satisfies the demands of science.
"The momentum for success is growing by the day. An agreement is well within reach."
The UN is aiming for a political agreement at the climate talks that would cover tougher emissions targets, climate financing for poor nations and the transfer of clean-energy technology.
Rasmussen said he thought a historic deal would be reached in Copenhagen.
"Over the last month, I have consulted with world leaders in order to pave the way for a successful conclusion of the climate change conference in Copenhagen," he said.
"My conclusion from these consultations is very clear. We sense strong support at the highest level to reach an ambitious deal in Copenhagen."
Nearly half of the Commonwealth's members are small island states which are directly threatened by rising sea levels caused by global warming.
Developing nations have appealed for financial aid from rich governments to help them counter climate change and reduce carbon pollution.
Meanwhile, on the sidelines of the summit, Canada agreed a nuclear co-operation deal with India, which will see it sell nuclear material and technology to the South Asian nation.
"Increased collaboration with India's civilian nuclear energy market will allow Canadian companies to benefit from greater access to one of the world's largest and fastest expanding economies," Stephen Harper, the Canadian prime minister, said.
"Canada and India will now take the necessary steps to prepare the agreement for final signature and implementation."
Canada stopped nuclear co-operation with India after the country diverted plutonium from Canadian-designed reactors to make a nuclear bomb in 1974.
The international community lifted a three-decade ban on nuclear trade with India last September even though India still refuses to sign the Nuclear Non-Proliferation Treaty.