Batteries are tricky. There’s (almost) no such thing as an off-the-shelf battery pack. If you go directly to a battery vendor (which looks like you have some experience) they’ll usually sell the packs uncertified. It’s up to you then to get them certified.
Have you considered cylindrical cells? The ones from Panasonic are pre-certified. Shipping lithium batteries still have limitations (by air) but they should be good to go.
You may want to try https://www.houseofbatteries.com and see if they have something off the shelf. Sometimes they do. In my experience, usually they don’t. They get their cells from factories in China so best to go direct if cost is a factor.
I’ve interacted with Tenergy in the past. They actually keep stock of cylindrical cells in the USA. I was looking into their 18650 and smaller offerings.