Provide ergonomic equipment

I have worked for this company for 18 years - I sit at a desk working on a computer on an ergonomic chair to eliviate the pain in my back - I also use an ergonomic mouse to help reduce the pain in my right arm due to repetative strain - 4 years ago the company was taken over and moved to a different location - the new computer system did not suite my ergonomic mouse - so before we moved a compatable one was ordered - that was just over 4 years ago - each employee has to have Supervision with their Line Manager and everything is discussed about workload, training and everything linked to the job - we are also asked if we are happy with our workstations - everytime I have mentioned that I still do not have a compatable ergonomic mouse and am told one wil be ordered - It has also everytime in Supervision been logged in my personal folder - I have been through Occupationial Health several times and have been told that I have to have the mouse - Each time I have attended my Doctors for medication it has been talked about with him and put in my notes - This Monday 07/10/19 - I had my back to work after 5 weeks off sick - It was mentioned again and I was told it should be here this week. What can I do?