0 Whither Johannes Van Der Kemp on the Heidelberg Catechism?

It seems that the two-volume set of sermons on the Heidelberg Catechism, lately printed in 1997 by Reformation Heritage Books, is almost entirely absent from the used book market (a couple of copies of a much older printing of Volume 1 seem to be available) and the only place I've seen new copies is at a UK-based Evangelical Press bookshop, where the going rate to get a set into the US is about $65 with shipping. Maybe I should just bite the bullet and pay up if I want this set, which I do... but if any readers have advice or know of used copies that are cheaper somewhere, I'd love to hear it :)