This is why I love HP. Any ways you could go to Dell and look up
Dell A720 printer
Since Dell has open the door for Ubuntu. Their pronters are just
remarked Lexmark's. Perhaps they have the driver for it.

All so try this
Download the driver from here:
www.downloaddelivery.com/.../...-CUPS-1.0-1.TAR.gz

follow these steps:
tar -xvzf CJLZ600LE-CUPS-1.0-1.TAR.gz
tail -n +143 z600cups-1.0-1.gz.sh > install.tar.gz
tar -xvzf install.tar.gz
rpm -i z600cups-1.0-1.i386.rpm
rpm -i z600llpddk-2.0-1.i386.rpm

Next check that these files exist
/usr/lib/cups/filter/rastertoz600
and
/usr/lib/cups/backend/z600
if they don't then copy them from a linux machine on which the above
driver has been succesfully installed and put them in those
directories.You may have to alter the permissions, I did.
If you don't have the files then PM me and I'll send them on.

Set up three links
cd /usr/lib
ln -sf liblexprinter.so.0.0.0 liblexprinter.so.0
ln -sf liblexprintjob.so.0.0.0 liblexprintjob.so.0
ln -sf liblexz600core.so.0.0.0 liblexz600core.so.0

I also created these links but Im not sure if they are necessary
ln -s /usr/lib/libtcl8.5.so /usr/lib/libtcl8.3.so
ln -s /usr/lib/libtk8.5.so /usr/lib/libtk8.3.so

Now set up in cups as normal.
Print away.

In case anyone is searching
http://ubuntuforums.org/showthread.php?t=49714 says the z600 driver
will work with these printers
Lexmark 5700 (black & white only)
Lexmark X1100
Lexmark X1110
Lexmark X1130
Lexmark X1140
Lexmark X1150
Lexmark X1180
Lexmark X1185
Lexmark Z513
Lexmark Z515
Lexmark Z715
Lexmark Z55
Lexmark Z615
Lexmark Z705
Lexmark Z605
Lexmark Z600
Lexmark Z25
Dell A920
Z65 (z65 driver)
Lexmark Z33 (z35 driver)
Lexmark Z33 (z35 driver)