Hi
Are you sure your cat cannot purr as some cats purr really quietly - i think purring is just a vibration in the throat - a bit like how our voice box makes us speak - so it is possible that your cat has something wrong with that - but if it is healthy in every other way, it does not seem right to operate just so your cat can purr - it would be like giving someone an operation because they couldn't laugh.
If you are not sure, speak to your vet.
I hope this helps.