If you view the coverage pdf files on the site you see there are 4 different nav units, 00, 01, 03 & 05 however there are only three main codes so either 2 units share the same discs or 2 discs share the same start of the part number but could have different endings.
Looking at Keywest's post it looks like 2 discs share the same start.
86271-70V290 and 86271-60V660 were not compatible. The numbers have to be in sequence, e.g. on my unit I have 08664-50860 the next updates were 08664-50861, 2 ,3 ,4
PZ485-L03EU-06 is a 2006 disc for a 2003 Nav unit. As you have a 05 vehicle I guess you have a 03 nav unit but could be an early 05 unit.
You could always ask your dealer for the price of a new disc, when they quote you ask what is the part number.
Also remember the PZ485......... code isn't printed on the disc so if purchasing from ebay always use the other numbers.
If you are purchasing from ebay remember that the Toyota models share the same discs for the full screen nav systems so don't just search for Lexus DVD. The very first DVD Nav discs (2000) have Lexus written on them but once the Nav unit came out for the Amazon they removed the branding so they didn't have to produce both Lexus and Toyota discs.