Camera Battery (4LR44 or PX28L) (Kirkley NR33)

I have a very old Canon film camera (35 ml SLR) that was recently returned by family after borrowing it 20 years ago for University work! I am planning to sell it but I need to test it still works, and there is a film in it too! Before buying a battery I wanted to see if anyone locally had one they no longer needed. Thanks if you can help. If I don't get a response in a week I will go ahead and buy some.