Left handed is best.
The G22 is not set up for a right side mag release. The Glock people would have to change the mould for the frame to accomodate that.
Why would you want one anyway? The mag release is an easy reach for the right thumb, and if you happen to be one of the lucky left handed people, the left index finger makes it easy to release.
Your only option is to put an extended mag release on your G22...