SDRAM has been replaced for all new systems by the faster and cheaper DDR RAM. As to why SDRAM production has stopped, it's not profitable for manufacturers to keep on mass-producing something that's going to sell only in small quantities for replacement or upgrade of "old" computers.
Tough, but that's the way it is in the computer industry. You could try Baazee.com.
there is a lot of sdram available at big apple in bangalore. i picked up some a few days back. its not true that sd ram production has stopped yes due to low demand the availability has become scarce.