well, hopefully someone here will have some spares then.....
the other option is to make your own... HIPs sheet is really cheap when bought in bulk and is endlessly useful for conversions and scratchbuilding
score a load of 40x12mm rectangles, snap em off, drill 6mm holes in half, glue on top of the undrilled bases and hey presto.... while it's time consuming (although you can do them quite quickly if making huge batches) the advantage is that you can make them to taste, with a different number of holes or different placement.... could even make them 40x10mm so you get the optimum side size when you're piling into BTB with a war engine or similar
IIRC Apoc made his own plasticard bases with 4 holes to make his world eaters go further..... just depends on how much time you have for these things I guess