Look at the back or bottom of the computer and look for a FCC # this number is a reference to your mobo.
as in xxx640x or xxx640c as c is an upgrade version and so on then go here and cross reference the mobo numbers and look at the pictures to match the mobo. There are some references to upgrades for each mobo and pay close attention as it is a noted item to use only SILVER plated connector pins and not gold ones.
This will be the same info for US and UK or CN
also I have found that this people are pretty good at suppling older type memory sticks at a very reasonable cost.