Well I hear buying graphite saddles can increase sustain - look into those. Also I found in WD music there is a special type of bridge block that can increase sustain - have a look on their site.
My Gear :
Fender American Strat in Metallic Red
EHX Big Muff
Boss ME-50
Boss SD-1
Fender 15 Watt Amp (Upgrade soon to a Marshall )
Red Furry guitar strap

John Frusciante - The Greatest Guitarist EVER
A well adjusted Strat played properly should have plenty of sustain. If you want more than a normal Strat you could use a compressor pedal (some pros and cons to that) or play with a little more gain. A lot of sustain comes from the amp. If you have a Strat copy then the pickups and/or wood may be the problem.
Quote by C_Miller
Is there one that I can get for my strat that can increase sustain?

What kind of Strat do you have? If it's a MIA then you've probably already got some good parts in it. If it's a recent MIM (2006-present) then it has a beefier trem block. If it's an older MIM then you might want to consider adding an after-market trem block like Callaham's. They're supposed to help add sustain because they're a lot beefier than the old zinc MIM blocks. They're also pricey and while it's pretty much agreed that they're a high quality part their value is very debatable. Some say they've installed them and not heard a difference, others say they've made a tremendous difference. I suspect it has a lot to do with the new part meshing with the guitar itself. Sometimes you just don't have good wood. You can replace the saddles too as a cheaper option or in addition.