Where can you get a commercially off the shelf CCCV lithium ion charger that allows you to set the voltage set point?
The ones with voltage set to 4.2v/cell are readily available and some with option to set for 4.25, 4.3 and 4.4 exist, but I'm not able to find one that let you choose fine tune with a lower value.
The strong drawback of a lithium ion battery is that they have a limited calendar life and it is strongly dependent on ambient temperature and terminal voltage. The most basic chargers out there will apply a trickle charge until it rises to some voltage in case the cell is very low, then charge in CC until it hits 4.2v per cell and hold 4.2v until current drops to a -pre-defined voltage.
Higher voltage cells that use anything from 4.25 to 4.4v CV values are used when the purpose is to get the most energy storage in pack. There are charge/discharge controller chips (often one does both) with dedicated saturation voltage, or selectable, but they only go up from 4.2v. I've never seen one that allows you to set a lower point. Charging to 40-50% and using a saturation voltage of 3.7-3.8v would be preferable for something you'd keep packed and ready to use in a emergency kit, which rarely sees use just like road flare.
Challenge has been finding a complete charger assembly, or a controller chip that allows adjustable saturation voltage under 4.2