One possible solution could have been making a lujvo from {me}, but it turns out that {me} has no rafsi. As for using {zei} (me zei ckaji or whatever), this doesn't look like a very appealing solution for such a basic and frequent predicate, as the resulting lexeme would be likely at least four syllables long.
Another possibility would be making an experimental gismu or a zi'evla. Running la gimyzba on the translations of "among" in the 8~12 largest world languages gives me {menre} as the best-scoring gismu form that doesn't clash with any official gismu. ("menre" mostly comes etymologically from the Spanish "entre", the Hindi "mem/men", the English "among" and the Russian "sredi".)