U.S. turn signals… allowable…???

Hello I am looking for someone who has installed a U.S. flasher or a conversion in his vehicle. Is there anyone who can make concrete statements about reliability (law texts). The search in the forum has brought 7 results, no specific information on the permissibleness. I have installed the U.S. versions in my Golf III in the original turn signals and achieved a good effect. If someone wants to have the original part numbers of VW then he can contact me. I hope that there is someone who can testify to the admissibility.