There's a lot of alternatives to leather items - wood, rubber, rope, plastic, PVC, etc. I believe there was a vegan SM toy site out there somewhere.
Just remember to respect others' choices in using leather items if you'd like your choice not to use them to be respected. :-)
NOT to criticise MsSM's response, and going off at a slight tangent...
Wood - is it obtained from responsibly managed sources?
Rubber - is it produced using cheap and/or child labour?
Plastic / PVC - non-biodegradable products obtained from non-renewable sources...
If we look closely enough, we can find justification for not doing anything, or producing anything, or using anything. To every problem there is a solution which has its own inherent problems. So perhaps it's best to retain a sense of perspective, and not get bogged down in any deep debates on the finer points of philosophy. Humans are omnivores: our bodies are built to consume meat, and for that to happen then animals must die.
Shouting and screaming rarely achieves its desired aims. Quietly, and calmly, each person must content themselves that they are doing the best they can, whilst accepting that human nature is a varied thing, and not all people think alike. The person alongside whom you work does not think the same as you, and it is not your right to force your ideas and beliefs upon them, no matter how heartfelt and sincerely you may hold to them. They are your truths, and yours alone.