On these opticals, you have to follow the links to the makers product site, and you can get their Product Spec sheets (usually PDFs) and they'll tell you their dimensions. For nstance, LGs are typically
Dimensions (W x H x D) 5.75" x 1.63" x 6.50"
Which was the first make that came to mind. Only problem is, they have some BlueBird Firmware issue right now. Haven't bought one myself in months ( I actually stocked up on LGs when they were dirt cheap, appeared to be a quality batch(s), and ddin't have the Bluebird thing.
I'd read any revs though, make sure the BlueBord thing has been addressed.
I think Lite-Ons are pretty short too.
Box 1:Xeon W3520 D0/HeatKiller 3.0/Feser Extreme 360 w/ 3x Gentle Typhoons 1850s/SWFT655/EVGA E760 Classified/ XFX GTX 285(Kool 285 block OTW)/CORSAIR CMPSU-850HX/ CM HAF /Corsair Domi's 3X2GB DDR3_2000/F1 Spinpoint 2x1TB-SATA/HT Omega Striker/ Build #2: Antec 1200/ E8500 @ 3.87 Ghz/Gigabyte P45-UD3P/ OCZ 4Gb Reapers PC2 9200/EAH4870 1GB/750W PCPC Quad Silncer/CM V10 1/2aTEC/ #3 Biostar 790GX/AMD 9950BE 3.2Ghz/OCZ Reapers 4GB 1066 /2.75Tbs of F1 Spinpoint/Corsair 550W PSU/