Help with information about rollators

I am currently researching a piece on rollators. Based on artistic research investigating the aesthetics and materiality of these essential but perhaps under appreciated objects I am struggling with finding some further information.
It is generally accepted that the first rollator appeared in the 1970s and was designed by Bernt Leander from Sweden. There is no record of a ‘first’ rollator and no history of the initial designs. Unable to find a person responsible for design and manufacture of rollators  I emailed the general Swedish inquiry contact at Invacare, the overall worldwide distributor but I have had no reply. I know that Dolomite was taken over by Invacare and their factory is in Anderstorp. A specific question I asked is regarding the range of colours available, particularly in 1997 in the Dolomite Futura range.
Thomas has kindly emailed his science/tech colleagues in Sweden but I wondered if anyone else might also have information. Academic texts are few and are mainly concerned with the effects on the joints of rollator users and effects on patients with other health issues and in assisting rehabilitation. There is very little about the actual object and its history.
Can anyone point me in the right direction for further information? Any help would be greatly appreciated