Yamaha-motor.com lists the part number as 1W4-.... This means that the C shoes have been supersceded to the 250D shoes, and means that 250D shoes must also fit.
My gut feeling is that the shoes from a 250C will be interchangeable with all of the other 'big drum' bikes of the era: DT1, DT250A, YZ250A/B/D/E/F, XT/TT500, etc.
I'm very wary of the cross-matches on a lot of sites. The G has a smaller rear brake than the F & the H, but is often shown as having the same shoes.