The best replacement for radio buttons is dropdown.

The best alternatives to radio buttons are rated as following:
★★★★★  dropdown
★★★★★  checkboxes
★★★  radial buttons
★★  check boxes

Your alternative for radio buttons is not listed? Suggest!
Speaking about radio buttons, one probably shouldn't forget about groupbox.

Other search terms related to radio buttons and their ratings are:
★★★★★ groupbox
★ form
You have in mind a companion for radio buttons and it is not yet here? Propose!



Google Trends

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radio buttons
dropdown
checkboxes