Heres an Idea, find a VG30 turbo from a Zed. You should be able to get the custom work fabbed for a few hundred, turbo will be very cheap if you don't buy it in the states. This is a very common thing to do with non turbo skylines, most of them only run 7-9psi from these turbos before they either highflow them or start replacing wheels.
Not sure if this is more then you want to spend but it's a pretty cheap idea.
If you are worried about the spool time on the VG turbos, look around for a T28 off of an RB20DET. If you get one off of an R33 you will get ceramic blades aswell
The little snails off of a Vr-4 is an option aswell. The only problem with these plans is finding a guy that does cheap fab work.