Create simple softwares to test portable Antivirus my company is developing

I need an experience developer to create simple malwares which we will use to test our new Antivirus. My company is developing an antivirus. We have being getting different malware samples from virustotal to boost our antivirus detecting ability. In order to make it function better, we need to test 2 types of malwares. These have not being made available to us from Virustotal. I need an experience developer to create 2 simple softwares which we will use to test our new Antivirus. The softwares should be undetected by other AVs, while we would work in our lab to make our AV detect it. The 2 malwares are 1. A malware infected pdf 2. A web browser malware