The best replacement for thumb safety is decocker.

The best alternatives to thumb safety are rated as following:
★★★★★  decocker
★★★★  no thumb safety
★★  grip safety
★  trigger safety
★  magazine safety

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Speaking about thumb safety, one probably shouldn't forget about shield.

Other search terms related to thumb safety and their ratings are:
★★★★★ shield
You have in mind a companion for thumb safety and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of thumb safety in all years. Click on graph for more.
thumb safety
decocker
no thumb safety