You can buy just the basket, if that is what you are after.
In any case post a picture of your existing strainer. Groco and Perko are two common brands. You can look them up and compare their looks with yours if you want to do that.
As I recall one has lugs that you turn to screw the cap off, the other has two thumb screw latches that hold the top in place, so they look very different.
The size is embossed on the cap, so all you need are the brand and the size to replace them exactly with what is already there.