Energy savings alone will pay for a new freezer inside a year, even if you had to pay for it!
FIRST, contact your power company and see if they have any upgrade programs, rebates and the like - many will cost-share and some will even buy you a new one for free.*
Then if that option is exhausted, get yourself a new chest freezer on your own nickel. Still a savings!
* At first blush, this seems insane. But if you grind through the macro-economics of buying you a new appliance vs. building new power plants to support your old appliances, this is actually a net win at the whole-society level. For instance if the same institution was paying for both the power plant an the freezer, they would have direct financial incentive to upgrade. With separate ownership there's a market inefficiency. Power companies and regulators just got together to correct that.