I don’t think that particular information is readily available. Only D/R/I split for all of early voting is available.
All Absentee BALLOTS for IA-2 RECEIVED by 11/8/16:
D - 80,100
R - 54,444
I - 45,087
Loebsack (D) - 198,571
Peters (R) - 170,933
So out of 369,504 total votes, 179,631 votes were cast early as absentee ballots (for which we know D/R/I split). For election day voters (which was 189,873 voters in 2016) - we do not know the D/R/I split.
Do you know where we were in 2016 on this date with absentees?
Ds now have a 25k lead which seems small as I recall.
I think the Rs have been doing better with absentee?