It's usual for plastic spinners to not be an exact fit on props, often requiring some careful removal of plastic from the spinner with a scalpel, coarse file or Dremel if you own one.
Slightly widening the slots for the prop blades in the spinner will often allow the spinner to fit correctly on the prop hub, providing that the spinner is not overly small. Make sure that when the spinner is fully fitted and tightened, that the prop sits clear of the spinner cut-outs and there is no distortion that may cause vibration. (It's vital that the prop blades are not scored or marked by the spinner). If you have to select a new larger spinner, then you'll be limited by the diameter of the cowl ring, so measure the cowl ring diameter and use that as a guide for the largest spinner that will fit.

Hope this helps.

C8