Charge pumps double the voltage. If you want to go to 2.4 times the start voltage, you will probably need a boost converter. They can be very simple...low number of parts. Depends on whether you have very tight efficiency needs.
What's your energy budget?
If you want to go the commercial plug and play route there is something like this manufactured by Cosel USA or also something like this from Calex. They run about $20 USD give or take.
You don't mention board mount or what you want but the above would be a good start. Slightly overkill on the current.
I have a rechargeable battery pack 2700 mah which will output around 3.7v to 5v my application requires 12v @20ma ideally the cheapest least amount of power wasted solution.
I have a rechargeable battery pack 2700 mah which will output around 3.7v to 5v my application requires 12v @20ma ideally the cheapest least amount of power wasted solution.