Mio has posted a Mio POI loader that allows you to transfer .csv or .xls POI files to an SD card and have them show up under My POI on your Mio device.
The POI loader may work with newer devices beyond those listed. I’m currently testing a Mio C720t and it worked fine with it.
I’m adding a link to this on my custom POI resource page, where you can find lots of POI sources to use with your GPS.
One little aside here. For those of you willing to go the extra mile, you can always buy a GPS with a low number of POIs, download more and add them to your unit.