I guess it depends how cold it is going to get but one of my annual guilty pleasures is Christmas markets and have spent a good few days ambling around in snowy Berlin, Prague, Vienna, ... purchasing a gluwein or two to "keep my hands warm".
I have never purchased any special bags for my insulin in cold weather. I just keep it well insulated in my bag or an inside pocket of my (or my partner's) jacket and have never had a problem with my insulin.
Until last year, my focus when in the cold has always been on protecting my insulin. Then I discovered my meter was also sensitive to (not very) extremes of temperature and errors when it gets a little chilly. Thankfully, it recovered but not before I swore a little. Since then, my meter also lives in the inside pocket. I threw away the case some years ago so it doesn't take up much room ... even a woman's pocket is big enough for the meter.
If you decide to purchase something for the cold, this is a scenario where Frio bags are definitely not the solution as they work through condensation rather than insulation.
Have a wonderful time in Iceland - I went about 10 years ago to celebrate a significant birthday in November and thoroughly enjoyed it ... and didn't even think of special insulin packaging.