I would think most machine shops would be able to make a set of spacers, it's pretty basic stuff. Here in the U.S., there are several companies online that will make custom wheel spacers ( you might check online). As far as building them, I have thought many times about making a rear set for my tractor but never have. At work, every time I looked at a pipe flange, blind or pipe spool I couldn't help but think that if you could find the right flange or blind, with little modification it would bolt right in as a spacer. The pipe spools we welded up were basically no different than many of the dual wheel adapters I've seen ( not applicable for what you need....just mentioning it).