I’m looking for a Chaparral/Vortex part, not Rotax, how can I find those part numbers?

Best place to start are the Vortex part guides, which are archived. You will have to buy these parts from an authorized Chaparral dealer.

https://drive.google.com/drive/folders/15jSxgzaaqlwfD6-VTnvTlrjk6QLIkQcQ?usp=sharing