If you want bespoke and thick, https://www.the-all-in-one-company.co.uk/
Or you can get them on Amazon, Walmart, Target, jumpinjammerz.com, footedpajamas.com, baby-pants.com, ebay, etc. There are many places online where you can get them.
If you are looking for the best, imo, would be the all in one company.
Seconding the All-In-One-Company, bought one from them after a long email conversation to figure out Things I couldn't due yto my visual impairment. Really great help, extremely great product too. On the expensive side, but definitely worth it in my opinion. I'd recommend asking for a fabric sample at first, certainly helped me choose what fabric to get my sleeper made of (went with the sweatshirt, I'm beyond satisfied!).
Its tight. i'm 5'9" 160lbs. you can't really wear a thick diaper in this cause the groin area is tight. not enough that you have a high pitched voice. Its seems the more I wear it it stretches out and becomes more comfortable. Buy one and see if its fits you and if not return it.
I just purchased a Lands End Footed sleeper, https://www.landsend.com/products/boys-full-zip-fleece-sleeper/id_289965_1055?sku_0=::ZAY in the size 20 and received it today. Man does it fit and is so warm. its nicely tight from my neck to my crotch. its looser from there to my toes. my size is 160lbs 5'9". I can't wait for the cold weather to come now. I've said before in this post I bought footed sleepers at sears in the size 14/16 that from the neck to the crotch is smaller but no to uncomfortable. I think a 18 would be just perfect.
Yes, I think the Land's End sleepers are great I have many pairs very well made, soft and warm. I also recommend Little Keeper Sleeper they have footed pajamas up to size 18 (in some models) but they are almost too big on me. I am also 5'9".