3 wheel walkers aid (Hanover BN2)

Hi I have an elderly neighbour who is in need of a 3 wheel walking aid, I borrowed a 4 wheel one from a friend but it wasn't right for her, she has tried a 3 wheel one and that worked perfectly, trouble is I can't find one for her to keep, she is 89 years old and independent, ( blooming stubborn) hopefully someone can help me help her. Thank you Derek