I see that Adafruit has released a Feather M4 board with two CAN ports and a single on-board CAN transceiver. This is based on a newer version of the same Arm processor that the Arduino Due has, which also has two CAN ports provided by that processor. But the Feather M4 is super compact and has the one built-in transceiver. Not as fast as a Teensy 4, but at 180 MHz that should be plenty fast for wrangling CAN messages.
If you provided your own transceiver for CAN0, you can have two CAN ports for bridging, sniffing, or other things. Also it can run CircuitPython for doing quick prototyping.