Here are some adult size Crew Style Sonic Socks by Bio World. These were sold at Game Stop in 2019. They seem to be about 7.99 for the pair, without a sale. They have red toe, heel and top cuff, gray stripes mid-foot, and a proflie running classic Sonic stock art on the leg part. The design is sewn into the sock, so it can't wear off. He is full color, but has a blue outline/border instead of gray or black, and also the pupil is blue. (no black thread used for the sock at all) It's good to see adults sizes socks that anyone can wear.

Here is a pair of Old Navy socks.
These appear in winter 2019 / 2020, and they fit adults sizes. They are in the Men's section of the store, and should be about 8.00 for the pair.
These are black, with a white & blue stripe and blue heel & toe area. They have a woven-in classic Sonic face with white border. It only uses blue & white thread for the colors. The tag is a little confusing, it says "Classic" but then also "Crew Socks Tube Socks". This conflicts, because a tube is not a crew, that's 2 different types of sock and 1 can't be both at once. It looks like it is a true crew, however because the sock is clearly shaped. (Tube is not) It's a good ordinary but solid design.

Bio World produces 2 more socks for summer 2020.
This is the factory photo, which shows they are in adults sizes to fit anyone (yay) and the designs are sewn into the fabric so they can't wear off. The socks are gray, with blue heel, cuff, and toe. The first pair has some neoclassic art for Sonic with feet forward and one fist held out. It has black double stripes for the foot area & below the cuff. The other sock has a scattering of all the same classic Sonic face all over the whole sock.
What's odd with the first one is they DO have black thread, so why didn't they use it for his eyes? He'd look better and sharper if they were black. (The second pair doesn't use black thread so it would have cost more to use it for just the eyes so you can see why they wouldn't in this instance) But, how much are these, and where are they sold?

And now for something slightly strange...
Here's a new pair of socks for 2020 by Bio World. They fit adults sizes/anyone but...they're kinda wierdly designed. Rather than having a typical "Sonic Design" they try to form his whole body AS a sock. And because he is not generally a sock-shaped person...it does not have all that much success. The face is ok as a wrap-around thing, but the belly dot is crazy wide and almost abstract. The arms appear coming out of the neck area, and the space between the legs is indicated with a distracting black rectangle that's also too wide. The shoes are foreshortened...wrapping around near the toe? Which is then blue again?
These are odd to look at, classic of style, and...I guess they're a novelty?