step recovery diode digikey

Is there is a place when I can buy SRD online?
I've tried with MACOM,Metelics,Micrometrics,Mpulse, but they don't sell online and they don't have distributors where I live

If you are just looking for a few to fool around with, sometimes they pop up on Ebay--you have to keep looking. I am not sure, but I would bet a laser diode has many of the same properties that an SRD would have (basic diode structure, conducts forward current, conducts reverse current until all chage carriers are depleted and then snaps off, etc). You can buy laser diodes at digikey.

For that matter, I bet a PIN diode can be used that way too, just go with a small capacitance one.