The HDMI to USB dongle (video encoder) usually is a wrapped MS2109 chip, you also want VGA to HDMI which is an ADC + HDMI transmitter, something like MS9282. I

The HDMI to USB dongle (video encoder) usually is a wrapped MS2109 chip, you also want VGA to HDMI which is an ADC + HDMI transmitter, something like MS9282. I guess it would be difficult to find a dongle that happen to have both chips, so the easiest way would be get a VGA to HDMI and plug it to the HDMI to USB encoder.