How can I find super-warm secondhand mittens?

Do you have any advice on where I should look or what I should look for?

Do you know of any very warm mitten types that are commonly available used?

Background: I am in the market for some super-warm mittens for next year. I would like to find a bargain on something used, even if it means sacrificing some quality. So I am periodically checking my local Goodwills, ebay, etc., biding my time and waiting to strike.

When it comes to the online marketplaces, it would help if I had some idea which products had the best reputation. I have some idea what brands are considered good, but each brand has lots of different types with different levels of insulation, and one brand may do one style well and another style poorly. Also, many of the mittens that are most highly recommended are either fairly new or fairly uncommon, so it’s hard to find them used.

Maybe this is too much to hope for, but I would love to find out about some kind of “classic” mittens that are durable, have been common for a long time, and are very warm. Maybe not as warm as ultramodern or specialty ones, but pretty warm.