My favorite brand flash is Sunpak. They sell 'potato masher' flashes but they are expensive. Instead I would go for one of their shoe flashes, which are packed w/ features like power ratio and bounce card. The one thing they don't have is the sensor on the camera. Of the cameras you have aside from the XA which is a beautiful outfit for what it was designed for. None of your cameras will do TTL but this is the next best thing. I would go for a Vivitar 283 of 285.
Each of these flashes have a cable accessory that will allow you to separate the sensor from the flash and mount the sensor on the hot shoe of the camera.

Francis in VT