Nope for purchase on DVD. You can Purchase a USB Thumb Drive on Apple Store. or call Apple to ask on that.
Also All I know is that you can use the Recovery Disk (CMD -R ) and download a copy of the installer. After the download you just need to specify a partition where you want to install the OS if you created a partition. Correct me if Im wrong Apple Guys coz Havent used the installer downloading from CMD R. Have already created a bootable one on a Hard drive.
Make a Time machine Back up before doing anything
The previously available USB stick came with 10.7.0. Apple doesn't provide the installer app on DVD. Whether or not it would install and run on your machine is left as an exercise. If it did work, then you could DL and install the 10.7.2 COMBO update. However, before you went that route, you should make a bootable backup/clone of your current installation and then test it.27" i7 iMac SL, Lion, OS X Mountain Lion (10.8.2), G4 450 MP w/Leopard, 9.2.2