Well, after looking at the 300-style replica rear sets on eBay, I could find them with and without shift/brake pedals and I could find them in left/tights sets but I couldn’t find them in left/right sets with shift/brake pedals.
Bizarre.
Same situation on AliExpress except you can also get them in black:
US $24.41 25% Off | Motorcycle Left Right Rear Foot Peg Brake Pedal Footrest Bracket For KAWASAKI VERSYS 250/300 NINJA EX250R Z250 Z300
https://a.aliexpress.com/_mOQ3TvS
Still, they’re new and seem pretty cheap compared to getting new 250-style rearsets. Ordering a left side with the shift pedal and a right side with brake pedal is probably the way to go.