The brushes with bamboo handles are for Japanese and Chinese calligraphy. The way those brushes are held is different, so the handle can't be tapered.
You can get those in Chinatown. But their bristles were designed for ink, so I don't know how good they would be if you push them around thicker paints.
I heard the Skyists brushes were originally designed for comic painters, who use gouache and acrylic, so technically they are suited to modeling paints.
I buy brushes from Blick Art too, and the bigger sizes are just fine.
I've had my share of experience with different series from Winsor, Princeton, La Corneille, Robert Simmons, Da Vinci and Loew Cornell. One thing in common with their spotters, they all have a rather large space between bristle and ferrule that was filled with sealant. Once the sealant is damaged, the arrangement of hair no longer stays in form, and you end up with curved or split bristles.
I'm assuming this is due to difficulties in manufacturering.
I got the Skyists from Ebay. The guy sells them once every few weeks (that's what he told me when I asked for more), he has to get them directly from Japan.
I got some other stuff from him. Here's a PE plier and a sprue cutter. Notice the angle of the cutting edge on the sprue cutter? I'm intrigued why these products are not available to us through retailers. They should be big sellers.
