bolt-on
From Longman Dictionary of Contemporary Englishbolt-onˈbolt-on adjective especially British English → bolt-on part/component/extraExamples from the Corpusbolt-on• Yet it should not simply be a bolt-on addition at the end.From Longman Business Dictionarybolt-onˈbolt-on adjective [only before noun] a bolt-on part can be added on easily to a machine, system, or service, without making any big changesIn manufacturing, bolt-on software may be used to supplement the core system. —bolt-on noun [countable]You can find more great cellphone bolt-ons at our online shop.