Amazon is loaded with versions of this. Others have mentioned higher-end ones. Here is an Amazon version:

Kattee Leather Canvas Camera Bag Vintage DSLR SLR Messenger Shoulder Bag https://www.amazon.com/dp/B00F5UDW2I/ref=cm_sw_r_cp_api_glt_fabc_JYGBTWN815XRHQ9VX254?psc=1