Not sure what it is you need but I do not find that cost outrageous for chrome finish to match.

You will need to stay with Kohler trim as each manufacturer has their own design regarding mounting points, etc. for the different trim pieces used. What determines which trim pieces can be used is the underlying shower valve assembly itself. Kohler has an old version (now out of production) of the Rite-Temp shower valves (example: K-304) and a newer design Rite-Temp valve (example: K-8300). You will have one or the other series of valves. (If you are a little turned around (buying trim first?) now will be the time to buy the basic valve to rough into the wall.) For any desired K trim piece, go to the Kohler website, find the trim and under 'Specs' pull up the 'Specification Sheet'. Their will be listed under 'Required Products and Accessories" the series of valve that the trim will mount to. (BTW, older K trim will mount to the new K valve bodies with a $12 adapter kit.) Hope this helps.

Ok thanks! The guy at the plumbing store told me I could get a delta valve, delta shower handle, and delta arm and then just attach my kohler showerhead onto the arm. Does that sound right to you? I don’t really undestand why any showerhead can’t attach to any arm 🤷🏻‍♀️

The guy at the plumbing store is correct, virtually any showerhead will attach to any vendor's arm because the industry has standardized on 1/2" NPT threads at the shower arm. The same applies to tub spouts. The differences that I spoke of pertains to trim that mounts to the shower valve itself.