Can't locate certain ram...

I purchased some of this
ram(http://www.ocztechnology.com/product...c_4000_gold_vx)
for my cousins computer about 6 months back, he wants to get another
stick but I can't find the same model for sale anywhere that isn't out
of stock, I can't even find OCZ PC4000 with the same timings, can
anyone recommend similiar ram that would work fine with it or link me
to the model anywhere? I can't find any that hasn't been discontinued.

OCZ Enhanced Latency Series Gold Edition 512MB 184-Pin DDR SDRAM DDR
500 (PC 4000) Unbuffered System Memory Model OCZ500512ELGEVX - Retail
is what I bought from newegg