I would not order them online as you do not know what you need until you have removed it. It is so much simpler to just go down to a place, buy shims, and return to complete. You still have to measure them again after reassembly and I've had a few surprises over all the times I've done it, must have wrote down a calculation wrong somewhere along the line. If this happens to you then you are stuck having to re-order and wait for shipping again. If not a local Toyota dealer, then check with a machine shop that does valve jobs as they will have access to shims as well. I don't know if they will sell them or not so dealer is the first place to check.

Keep in mind also that you can sometimes remove several shims that are out of spec and after measuring, find out they are the exact fit needed on the other valve. You will still need to buy some but I'd say about 1/2 of all that are out of spec can be resolved this way without buying a new shim.