I'm not sure of the status of the Wells-CTI company, but availability for their line of test sockets seems to be somewhat unreliable.
But I was obtained the follow items at good prices from seller fullfusion, on DHGate.499-P38-20 TO-261-4 SOT-223-4 499-P35-20 TO-252-3 D2Pak 3-pin 499-P36-20 TO-236-3 SOT-23 3-pin 499-P44-20 SOT-23-6, 6-pin 499-P37-20 SOT-89
These test sockets mount on a PCB, and have a convenient clip-handle to release the part. fullfusion also stocks high-pin-count sockets.
The RIS-767 test-bench pcb includes the last two types, for easy use with a 2-channel SMU, and I'll add the top four in the next batch.