I have a self-portrait assignment for photography class, but the Pentax k1000 that I'm shooting with doesn't have a self timer. I have a shutter release remote that I use for my other film cameras, but I'm not sure if this one has a sensor.
It's not so much a sensor as a mechanical connection — no electronics are involved — but the shutter button has a screw socket for a shutter release. See a video demonstrating this with a K1000 on youtube.
Or go for this bulb trigger with a 20-foot cable for $15.
PS: I've used none of these exact items, although I have a similar one in a box somewhere. Any of 'em should work for you. It may or may not be what you already have for your other cameras — if what you have looks similar, give it a try. (If, on the other hand, it's electrical, let alone electronic, that's not right.)
You can get a mechanical self-timer that screws into the shutter release button, just like a cable release. I used one like this on my K1000:
You lock it with the small red button on the side, then wind it with the metal bit you see on the top. The large red disc is a flag which you rotate around the axis underneath the black button. The farther you rotate it, the longer the timer runs. When you unlock the mechanism with the small red button, the clockwork mechanism inside slowly rotates the flag back to the starting position while simultaneously pushing out a pin, which trips the shutter. The pin comes out the small hole you see in the shaft in the lower right corner of the picture. You can also see the threads that screw into your camera's shutter release button.
The only tricky part about using this sort of timer is that you have to adjust the length of travel for the pin using the two knurled collars you can see on the business end of this beastie. If you set the length of travel too far, the timer hangs up when the pin bottoms out in the shutter release's hollow. If it doesn't go far enough, the pin doesn't trip the shutter at all. And if you get it somewhere in the butter zone but not close to its best depth, the shutter trips before the red flag hits the bottom of its travel, so you get surprised by the early shot.
(That's why the flag is large and red, by the way: so you can see when it's about to trip the shutter from a distance.)
I couldn't find new ones still being sold at either Amazon.com or B&H, but there's a bunch of them on eBay.