Shiv Spacer Question

My Shiv came with two 20mm spacers. They are not the typical round spacers but more of an aero look (kind of “U”-shaped). I want to take 15mm out of the height. The question is, how do I do that without just replacing one of the the Specialized 20s with a typical round 5? I could do this, but it would look odd above the stock 20. I asked my Specialized dealer and they didn’t know the answer. I can’t believe that Specialized would only make those spacers in the 20mm size. Has anyone encountered this? What did you do? Am I just missing something obvious and asking a real dumb question here?

I’m guessing they only have 20mm spacers since the rocker in the stem and other adjustments cover smaller position mods.