The best replacement for 90mm is tokina 100mm.

The best alternatives to 90mm are rated as following:
★★★★★  tokina 100mm
★★★★★  88mm
★★★★★  sigma 105mm
★★★★  canon 100mm
★★★★  nikon 85mm
★★★  105mm
★★★  nikon 105mm
★★  canon 100mm macro
★★  70mm stem
★  sigma 105mm macro
★  60mm
★  nikon 60mm
★  150mm
★  canon 60mm
  100mm macro
  100mm
  nikon 85mm 3.5
  tamron 60mm
  nikon 105mm macro
  75mm
  tokina 100mm macro
  sigma 150mm

Your alternative for 90mm is not listed? Suggest!
Speaking about 90mm, one probably shouldn't forget about raynox.

Other search terms related to 90mm and their ratings are:
★★★★★ raynox
★ extension tube
You have in mind a companion for 90mm and it is not yet here? Propose!



Google Trends

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90mm
tokina 100mm
88mm