All the vibrating alarm clocks I could find do not sync with your phone, and have to be set manually. I thought about getting an Arduino, but then I will have to build the whole thing by myself. The only logical conclusion I could come up with is to get a programable vibrator. But most of them are either very expensive of look too much like a vibrator (sus).
This is the closest I got: https://www.amazon.com/dp/B09NNFPHXG https://www.amazon.com/dp/B0CD7FPFQ5?th=1
Try a Mi Band. I usually don’t recommend Xiaomi products because of their heavy tracking and intrusiveness, but if you only use the band during sleep, you should be fine. If you already have the know-how (which I suspect you do), you can control it yourself through Bluetooth, and the band will erase all data it holds once transmitted.
Some of the Mi Bands work pretty well with GadgetBridge, which would block their ability to phone home. There’s a list is compatible devices somewhere on the GadgetBridge wiki.
Throw in a leg strap, and this becomes the best bang-for-the-buck solution.
Or an Amazfit band (Mi band but the more western-sold version). The Band 5 is pretty cheap and has a decent buzzer.