Did the designated man live out the year?

A curious Chizkuni in parshat Acharei Mos. The pasuk states:

כא וְסָמַךְ אַהֲרֹן אֶת-שְׁתֵּי יָדָו, עַל רֹאשׁ הַשָּׂעִיר הַחַי, וְהִתְוַדָּה עָלָיו אֶת-כָּל-עֲו‍ֹנֹת בְּנֵי יִשְׂרָאֵל, וְאֶת-כָּל-פִּשְׁעֵיהֶם לְכָל-חַטֹּאתָם; וְנָתַן אֹתָם עַל-רֹאשׁ הַשָּׂעִיר, וְשִׁלַּח בְּיַד-אִישׁ עִתִּי הַמִּדְבָּרָה.

21 And Aaron shall lay both his hands upon the head of the live goat, and confess over him all the iniquities of the children of Israel, and all their transgressions, even all their sins; and he shall put them upon the head of the goat, and shall send him away by the hand of an appointed man into the wilderness.

And Chizkuni writes: בְּיַד-אִישׁ עִתִּי: If is found in midrash: itti {denoting time}-- that he has reached his time to die, within that year. For behold, he who conveys the goat does not pass the year {alive}. Therefore, they would choose a man who had reached his time to die within that year. And the science of the zodiac was easy in their eyes.

My strong sense is that Chizkuni's quote of the midrash end before the word "For."

Thus, itti {denoting time}-- that he has reached his time to die, within that year.

And the rest is Chizkuni's interpretation of that midrash. I have not been successful in tracking down that midrash.

I would disagree with Chizkuni's interpretation here. He is transforming it from a single derasha into a double. The source for the fact that he would not live out that year is the word itti, that he was thus with a fixed time. Instead, he takes this as background, as a given, and claims that with astrological knowledge they chose someone who would die anyway within that year, so as not to condemn a man to death -- and that itti was "that he has reached his time to die" already before being chosen. Is this then to be the instruction of the Torah, to use astrology in this way because of what would be known to happen? I would hasten to add that even if this were the intent, one could choose a sickly individual, without having to resort to astrology (a science of those days, rather than a superstition).

We can compare this to others who did not live out the year. The Tzeduki Kohen gadol who put the ketores on at the wrong point, in accordance with Sadducee beliefs did not live out the year. And the gemara in Bavli Yoma 9a reads:

אמר רבה בר בר חנה אמר ר' יוחנן מאי דכתיב (משלי י) יראת ה' תוסיף ימים ושנות רשעים תקצרנה יראת ה' תוסיף ימים זה מקדש ראשון שעמד ארבע מאות ועשר שנים ולא שמשו בו אלא י"ח כהנים גדולים ושנות רשעים תקצרנה זה מקדש שני שעמד ד' מאות ועשרים שנה ושמשו בו יותר משלש מאות כהנים צא מהם מ' שנה ששמש שמעון הצדיק ושמונים ששמש יוחנן כהן גדול עשר ששמש ישמעאל בן פאבי ואמרי לה י"א ששמש ר' אלעזר בן חרסום מכאן ואילך צא וחשוב כל אחד ואחד לא הוציא שנתו

such that for a long stretch, the kohen gadol each year did not survive the year. But this was punishment, or not being of the proper level. In Yerushalmi Yoma, we see that for a similar span, the conveyor to Azazel was unsuccessful, with the goat running off, only to be eventually consumed by desert dwellers. I have a theory ... perhaps a conspiracy theory, but perhaps not ... that this too was the result of Sadducees, who interpreted the pasuk to mean that it should be released into the wilderness. Perhaps I will post more on this theory later. But anyway, perhaps this midrash took its cue from this gemara about kohanim gedolim of Yom Kippur not living out the year.

What would be the implication of itti almost meaning "condemned"? Perhaps as immediately above, but this would seem to be assuming the unworthiness of the individual. Perhaps the idea is that not only the goat was being condemned to death, but also he who conveyed it. Especially if we understand Azazel as Samael, this might be interpreted as a sort of human sacrifice. Or being impacted by the interaction with Samael. Or the person as a type of atonement for the community. Chizkuni does understand it as a bribe to Samael, and as such, he is mitigating this human sacrifice by choosing someone who would die anyway, and reads this into the pasuk. I don't know, but this midrash makes me uncomfortable.

Any other suggestions as to how to understand this midrash? Any leads on where to find this midrash, other than Chizkuni. Where is the Kli Yakar who discusses it?