I use Boxer-primer RWS 10,75x68 brass, trimmed to length, as I have a few handfulls. But I have also made useable cases from 9.3x64 by swaging /turning down the bases. This is the main reason I refused an offer to rechamber this barrel, as the Brenneke cases are easier to get in a pinch.
No,I do not have an original 10.75x63 cartridge. Only after I had solved the loading problems I saw one at a gunshow, but the asking price was more than I invested into the rifle!
I do not intend to take this rifle to Africa, as I have 9.3x62s and a .416 Rigby too.