I bought a universal microchip scanner, so I can now put in microchips. I have purchased SaveThisLife chips, which do not have any registration fees, and can be searched on Google. If you are interested, the procedure can easily be done at home (it's just a large needle, inserted in the area near the scapulae; most cats tolerate it pretty well).
The cats I have used this chip on, including two of my own, have barely noticed the placement of the chip. This chip is international compliant (it's numeric only).
And apologies that I haven't figured out how to put references on here, but you will find several reviews on Google.