Here are two potential solutions (in no particular order).
1. FSR FL-200 with accessory plate number MMS-FL200-4 https://fsrinc.com/documents/spec-sheet/8556-lit1555b-fl-200-spec-pdf/file (please see page 4 for this plate)
2. Legrande/Wiremold Evolution Series 4-/5-gang Floor Box EFB-45 with adapter plate EFB8-22GMB http://www.legrand.us/-/media/products/resources/wiremold-products/floor-boxes/commercial/steel-concrete-floor-boxes/efb-evolution-floor-boxes/ed1770r2.ashx (please see mounting diagram on page 4 and accessory plate on page 5)