Its almost a requirement to upgrade from the shimmed factory buckets to factory shimless buckets.   The stock shims have a tendency to fly out of the bucket under high rpm operation.

These are the toyota part numbers for MR2 Spider shimless buckets which are compatible with 2jz.

All measurements of buckets are in mm.

13751-46030 5.06
13751-46040 5.08
13751-46050 5.10
13751-46060 5.12
13751-46070 5.14
13751-46080 5.16
13751-46090 5.18
13751-46100 5.20
13751-46110 5.22
13751-46120 5.24
13751-46130 5.26
13751-46140 5.28
13751-46150 5.30
13751-46160 5.32
13751-46170 5.34
13751-46180 5.36
13751-46190 5.38
13751-46200 5.40
13751-46210 5.42
13751-46220 5.44
13751-46230 5.46
13751-46240 5.48
13751-46250 5.50
13751-46260 5.52
13751-46270 5.54
13751-46280 5.56
13751-46290 5.58
13751-46300 5.60
13751-46310 5.62
13751-46320 5.64
13751-46330 5.66
13751-46340 5.68
13751-46350 5.70
13751-46360 5.72
13751-46370 5.74

You can easily purchase these from Curt @ Elmhurst toyota or the supra store.