My personal experiences in the last few years, I have used the clear, zipped, expandable bottom, cosmetic case.
Logan is my base. I've never been questioned or asked to change out to a zip lock quart bag. I've flown through Heathrow & FCO; no one blinked an eye. I've also flown through other Domestic airports in the last few years, & again, no one said anything.
I got cases at a store "here" in the New England area called Christmas Tree Shops and That!. They sort of resemble a larger envelope. They are 100% see-through right up to the white zipper. They pretty much meet the "measurements" even though the cosmetic cases are a little bigger than a zip lock.
They don't stand out (like neon) where a security person would need to take out a measuring tape. They have the 'soft-bottomed' expandability & a decent zipper. I think they are sold in-store only. The stores also have a huge selection of travel items for those who don't want to decant or need something unusual.
Check out TJMaxx & Marshall's for the ones that are similar but come with little jars & bottles for decanting. Make sure to stay away from the overly decorated ones or the ones that are too rounded or too hard plastic. The simpler, squarer, the better. Walmart has all kinds of travel sized items.
Unless your mousse is very specific for your hair needs, maybe consider a travel spray gel/travel mousse. Nexxus is pretty good. I found TRESemme to be drying. I use Garnier products & decant my own spray gel - get a little funnel at Walmart & slowly pour the gel into a 2-oz bottle. Yep, because it's thicker, it will take its time. Make sure to not let it build into a glob in the funnel, lol.
To be on the safe side, take a couple of the sturdier zip lock baggies just in case the TSA or security at other airports tell you to change out.
Keeping organized is key. For the little jars, I decant any creams/makeup, etc. I "stack them" & tape them together so they stand upright in the bag - allowing more room. I usually use 2 oz. bottles. There are also spray bottles that size too. They can be slimmer. Eyeliner is a pencil, blush is a travel sized compact, lipstick, gloss - brushes, sharpener & lash curler don't need to be in 3-1-1. (Extra liquids go into the checked)
Check out your department store makeup counters. Lancome & Estee are good about giving out samples of a favorite blush, eyeshadow (if you wear it) & travel mascara. Those are usually in the goodie bags when they have their promos. Sometimes, they have those purse samples left over.
Years ago, I was surprised to learn that mascara needed to go into my 3-1-1. No biggie, it fit of course. I decant a liquid hairspray into bottles. I have longer hair, so if it's just not doing its thing that day, I can use a hair clip and wear it up or use a pony tail holder for a lower pony style -- the holders are made to look like little rosettes -- I get the muted tones -- they come in a set of 3. I take black & brown headbands -- they have a fabric on them which makes them a bit dressier. All can be found at Walmart. I think? they are made by "Goodie" or a similar brand. Not expensive. They sell travel size deodorant or solid.
I check one bag & carry on a smaller bag with 3 days worth of clothes & my tote/purse for valuables -- makes it easier to take into a lav. 3-1-1 bag is good for 5 days.
With just a carry on, it's a bit of a game changer. I stay in one place when traveling so it's easier for me to take two bags & other things I favor. For those on tour or staying 2 days here & there, then it's probably more cumbersome.
Europe will have Farmacias, discount stores & supermarkets selling things you may need, forget or don't want to carry. Yes, sometimes, it can be more expensive, but, you have to 'weigh' what's important to you.
Play around with things; see what works. Maybe some of my travel ideas may work for you. Good luck.