Is this a one-off requirement, or your normal daily operations?
Invest in a source of external power (start stick), and the rest of it becomes obvious - a single overtemp will cost you more than any practical investment you can ever make in the proper equipment for the conditions - and I'm not talking about just the cost of the overtemp, you need to include travel to your location, maintenance activities to remove and replace the turbine, rental module, and then changing it back out again. If you are consistently operating in these conditions, you will want to invest in a quality set of covers specifically for the 206. Removing the battery and bringing it inside and applying your trickle charge will make sure you also have a good battery to begin with.Heating the engine and transmission area will also assist in keeping everything functional. A start stick will also allow you to take your external power with you, having experienced a hot start on the top of a mountain after a brief shut-down one day, I can tell you that the logistics and expense of rescuing our crew and resolving that incident where the helicopter became entirely buried in snow and we were there replacing a module is not easily within the resources of a typical small operator. I had every kind of resource you could imagine, and in retrospect, I should have just slung it back to town!. Also, make sure you have appropriate survival equipment with the aircraft at all times.