They don't look too hard to make spec in copper.... i'd start with some 2nd hand copper pipe from the scrappie don't know if you can get it in 38mm id if you head into a chandlery they should have softwood bungs that you could use as a plug for shaping against and a bit of hammer work solder a bit of brass mesh into the end for the filter just anneal it first.... sure spun would get you a better shape quicker e.c.t. but for a small outlay