I've been searching any reliable database I can find (only in English, unfortunately), but I can't seem to find any kanji with a ジェ reading. WWWJDIC doesn't list any, so I figure it's hopeless, but there are only around 6000 kanji on KanjiDic, right? If I'm not mistaken, there are tens of thousands of ultra-rare kanji, the elusive 表外字 which I've been unable to find a database for.

Anyways, the reason being, my name is ジェイソン, and though my friends assure me that using a ジ kanji alongside an ェ would work just fine, I'm being stubborn and want to squeeze ジェイソン into two or three kanji if it's possible. It's prettier that way ^_^

Anyways, thanks in advance for any help anyone can give!

There are no kanji read as じぇ. Afaik the sound doesn't even exist in the Japanese language other than in loanwords, although maybe I'm having a brainfart.

No one will be able to read a nonsense western kanji name anyways, so you might as well pick any kanji you like (perhaps a literal translation of your name) and give them furigana.

As Jarvik wrote, only load words usually written in katakana use ジェ. There are plenty of characters pronounced jie in Chinese but the pronounciations all got japaneserised (?) when introduced to Japanese. You could go around using a real chinese pronounciation of a character (for example 街) and explaining that to everyone you meet but it'd be rather pretensious.

You're not going to find a じぇ kanji, no matter how obscure. Your best bet, and the typical practice, would be to us a JI kanji and an E kanji, like your friends suggested.

You could go back to the Greek roots of your name and use イアーソーン.