I haven’t seen a specific close proximity sensor but I inadvertently made one once. I bought several of the Iris motion sensors a few months ago when they were on sale and buy 2 get 1 free. I wanted to try adjusting the sensitivity through various means in order to use outside. One of my tests was to try covering the center lens with different materials to lower the sensitivity. I tried everything from clear cling wrap to electrical tape. Some of the more clear items (wanna say like clearish scotch tape) reduced the motion sensor detection to like 3 or 4 feet or maybe even less. Since this wasn’t my end goal I didn’t pay much attention to which did what. It’s certainly something worth testing out for your own purposes with little risk as the sensor is cheap and tape won’t break it.
I’ve been to lazy to install it but in the end I created a snoot ie tube over the PIR sensor to create a very focused detection beam for the Iris unit. I just need to install it out front and properly aim it. The end game is to eliminate the repeated false detection’s the Arlo gives me out front and use this one some how to record front door video. I used some shrinkwrap for my snoot but may ditch that as I found the tube the little vials of superglue come in seem to be the perfect size. this way the whole thing is white and the tube is more durable than the shrinkwrap.