70.3 Aquabike

The Ironman Branded races tend to be a really big field of athletes in the range of 1,500-2,000.  Because of that you typically don't see IM events that have a HIM & IM option at the same event but rather a HIM at the venue in the spring and a Full IM at the venue in the fall or via versa.  Everyone at the event is doing the same thing which makes the competition better and reduces confusion on the course. 

About every independent race that I have seen offers some type of variation of the race with either a Duathlon, Aquabike, or Aquathon options.  At some of the independent races you also see concurrent distances where they will start a 70.3 at 6:30 AM, an Olympic at 7:15 AM, and a Sprint at 8:00 AM, etc.

I have only done two IM branded races and I don't think either of them had options for Aquabike.  I could be wrong though.    If you are looking for an aquabike event you might have better luck at a smaller independent race.  You can search race information on the Ironman website though to see what options are offered at each event. 

Note:  There IS an Aquabike option at the River Roux Triathlon on October 9th in Louisiana.  I only know that because that race has been on my wish list for a few years and I have been checking the race site every week for the past two months because I think this is the year I am going to finally do it.   They Dropped the 70.3 Option this year which is what I wanted to do but hopefully that option can come back when races are a more sure thing.  Oh....I have done the Redman Triathlon several times.  It is a September Race in Oklahoma City.  They have 70.3 and Full Distance Aquabike options.  That races was canceled this year due to covid uncertainties though.  Have you looked into the Titanium 70.3?  That one is in Michigan (Much closer to you) and shows to have an Aquabike option.  I met the race director of that race at the Redman Tri in 2019.