In the early 1920s, the Lewis bicycle factory and showroom at 111 Gawler Place reverted to trading under the pre-1907 name of "Lewis Cycle Works, Limited", while the motor business continued to trade at Gawler Place South as "Vivian Lewis, Limited". I believe that Cyril Lewis, Vivian Lewis' son, was managing the cycle business at this time.
By 1925 the Lewis Cycle Works Ltd was diversifying, and in their directory entry for that year they described themselves as "Manufacturers and repairers of Cycles, Motorcycles, Delivery trucks and Invalid's chairs". In 1928 they added "Agents for Atwater Kent Radio".
Of these diversions from the bicycle trade, the wheel chair business was to be the most durable, ultimately outlasting the bicycle business. A range of chairs were produced, with various forms of motive power including (in at least one case) a small petrol engine.
Originally manufactured by the Lewis Cycle Works Limited, various other companies seem to have been involved in wheel chair manufacture in later years, including Lewis Chair Industries Ltd (at Ashford Rd, Keswick and Streeters Rd, North Plympton in the 1950s), Lewis Industries Pty Ltd (Streeters Rd, North Plympton in the 1970s) and Lewis Wheel Chairs Pty Ltd (?) who existed in Wright St for a number of years after the Lewis Cycle Works Pty Ltd ceased operations in 1975.
Additional information would be most welcome.