Just For Ponies is a good go-to for all things little.
I’ve found for blankets, it’s helpful to find ones labeled as pony blankets specifically, not just ones in shorter sizes. Otherwise often they are pony-sized in length but not in height so they come down way too long on bellies. I have a small pony and I like Amigo and Mio blankets best for her. I tried a SmartPak blanket for her and it was so long it could have kept her knees nice and toasty. It was a 60” blanket that was cut for a 16h horse.
I have two Smartpak pony bridles, both Plymouths, and they’re both wildly different in size. They were purchased two years a part. One fits the small perfectly, one fits mediums and dainty larges. The quality is decent for the price but I hesitate to recommend them because I don’t know what fit you’d get!