Try searching for "free dwg blocks" or "free autocad blocks" and you will find many objects in DWG format. Here is one site I found:
https://dwgmodels.com/You can then use the ODA Converter to convert the file from .dwg to .dxf. Choose .dxf 2013 version or earlier
https://www.opendesign.com/guestfiles/oda_file_converterI hope that helps.
Thank you google translate!
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