I've seen quite a few ER-like collets (DIN, OZ, VB, TG, ...) on the Vertex catalogue that I got from some UK vendor (cannot recall which, probably Chronos, ARCEuroTrade or RDG) in bedside reader form.
They're complete with drawings and specifications.
They can be seen on the Vertex site, too
www.vertex-tw.com.tw [enter] -> "Products" -> "Tooling system ER Collet ..." though browsing there is a bit slow - don't hold Your breath while waiting for a page to appear.
HTH
Marcello