I found an already existing connector which is still in production and similar to the Atari Homecomputer SIO connector of the data cables. Current price of original Atari cables are 20 dollar. I have about two big boxes full of them as (and about the same number of 1050 power supplies but this is another story) i bought nearly every available cable seen in the last years 

The found connector is not useable as delivered by manufacturer but after some modifications fit quite well on every SIO port I've tested. Price is as usual not very high. a complete cable 1 feet with two connectors costs only a fraction of current one.

I will produce a production ready prototyp and then decide if worth to start bigger production or not.