Hello Charles
When doing the research please remember that the arranger name did not come about till around the 90s, so also search for single manual organs and single and/or portable keyboards before then.
Regarding Wersi their main instruments were always Organs (And to a large extent still are) therefore Arranger keyboards do not feature heavily, however 3 models that worked toward Arrangers were the Keyfox, Pegasus (Early 90s) and Abacus, (2000) but even these were really Single Manual Organs and a true Arranger Keyboard was not released until 2003 when the Ikarus was introduced. (This is why in spite of the Ikarus larger keyboard, the price is significantly below the Abacus)
BTW there are rumours circulating that Wersi are going to introduce a board under the Ikarus, which if true should be interesting. (Please remember the last part is a rumour with as yet no solid supporting facts)
Hope this helps

Bill