Keeping the spelling 'Kristtorn' while sounding like 'Kriston' - possible with diacritics?

Words and letters do not produce any sound, people do using their speech organs and the pulmonic airstream.

There doesn't seem to be any straightforward way to elicit the desired pronunciation /ˈkrɪstɒn/ through spelling, ton at the end of a person's name or in placenames is typically realized in a reduced form such as /tn̩/. Anything with an r will be mispronounced in rhotic varieties of English.

Perhaps Krist-On could work but I'm afraid yours will be the lot of Rupert Psmith, Wodehouse's character, that had to tell people how to pronounce his name and specify that the p was silent as in pshrimp.