2sa1993 cross

Well, I went to the Digi-Key site and did some filtering.

in stock
Hfe 100-300
Pdiss 0.3-1W

and maybe a couple more that I can't remember

Came up with 2n3906.

When cross referencing parts that are not exactly the same you have to decide what features or characteristics are critical.

If your part ran at 45V (rated for 50) then the 2n3906 would not work (rated for 40).

If your part was used as a switch with a Ic/Ib drive of 10 then a Hfe of 100 is not really needed but low Vce sat would be important.

So to get a cross reference that would be the best fit (compromise) you need to review what the transistor is doing...schematic.

Sorry I can not help more without more information. (schematic and use)
What is it used for? If it is turning an LED or relay off and on, you can use just about anything. If it is in a low noise preamp signal path, maybe you need more selectivity.

I haven't looked anything up, and 2N3906 might work fine. But i will warn you, all the 2SAxxxx transistors will have the legs in different order from the 2Nxxxx tpes. You can swap them, but will need to turn the part sideways to get the legs in the right holes.