Interesting, I have phpize in /usr/local/psa/admin/bin/phpize.
If you are on a RH type distro, you may be able to find a php-devel for your distro at atomicrocketturtle.com
If you have yum installed, just configure your channels for ART's (follow directions at bottom of each download page) and do a:
yum install php-devel
I didn't read all their instructions, glanced over them. I prefer Leibert UPSs myself.