Like Stupus stated above to do what you are wanting is possible, but the results aren't going to be very good and would take up additional space and cost.
The simplest solution is to use an old VCR that can de-modulate the signal and provide you with a composite ouput. From there, you can get a cheap composite to HDMI upscaler/converter unit. But keep in mind that most of those devices will stretch the picture unless your TV is able to compensate for this on its own. (Some can, many don't).
Also you will get some lag in the response of your actions when playing the games in this manner. But how much lag you get in response will depend on the TV processing the image and the converter.
This is why so many have started to get AV mods done to their older systems so that with at least a native composite output, you can then use something like the RetroTink2x to eventually get as lag free an image as possible to your TV.
You could still go with the VCR idea and combine that with a Retrotink2x to get the composite image from the VCR video out to the RetroTink2x and then have HDMI back to your TV. Just depends on your space for having everything setup and money to spend.
Here is one of the cheaper composite and s-video to HDMI adapters from Monoprice. I paid twice this for mine when I first got it back in like 2012, but this one is an open box one they have on the cheap. You still get lag in using this and it will still stretch the image our of proportion but it does work and work well. I was actually using one of these exact ones along with a large s-video and composite AV switcher for 6 years before I upgraded to more expensive solutions.
Edited by -^CrožBow^-, Thu Dec 6, 2018 9:51 AM.