Exhaust manifold parts

[Jos]

Can any of you guys who have made your own exhaust manifolds point me in the direction of a supplier for butt weld sections for 1.5" TUBE (not PIPE)
Being harshly educated in the difference between tube and pipe sizes, butt weld fittings for pipe seem to be easy to get, tube sized sections - somewhat harder.

the M42 manifold is 1.5" diameter and about 1.5mm wall, I need to replace a couple of sections on it. Or would I be better changing it to a similar pipe schedule (1.25" Schedule 5 being about the closest)

Thanks