What I'm looking for are is just the microchip reader itself, one that spits out the chip code as the pet comes near the sensor. I can see lots for sale on amazon/ebay but they're all fully functional readers with batteries, displays, etc. The Wikipedia article https://en.wikipedia.org/wiki/Pet_chip lists the various types/frequencies they operate at. The RFID readers you have for sale seem to operate at 125khz rather than 134.2khz which seems to be the pet standard.
Having the reader would allow us to automate doors, feeders, alarms, etc..