I can most probably get them for you but will need to know the center bore of your aftermarket wheels. If you take one off, it is usually stamped into the back of one of the spokes. You will be looking for a number, I would have thought around the low 70's. If you can find this out and let me know i can get some for you. If you can't, pm me the make and model of wheel and I should be able to find out for you and get you the required spiggott.
Another thought though is that you may have just lost some balancing weights off the wheel while they have been stored....or they were originally balanced incorrectly or on an uncalibrated machine.
You will be able to check if you need spiggots by either looking for the center bore measurement on the back of the wheel or when you offer the wheel up to the hub, you will be able to move it up and down on the hub...ie: there is a gap between the hub and the center bore of the wheel. The spiggots centralise the wheel on the hub and if it is even 1 or 2mm out, it will cause vibration.
Let me know