Originally Posted by
fietsbob
26-25.4=0.6, so use 0.3mm shim stock, which is what Nitto's pieces offer.
OP states he tried the Velo-Orange shims, which are essentially the same as Nitto's:
VO Stainless Steel Shim 25.4-26.0mm, 35mm or 45mm width
Not sure why he still has problems, but the proper size stem should be a solution.