You can get padded envelopes at most drug stores and general stores, or you can just recycle a box that has been laying around your house. (relevantmagazine.com)
Our office manager started buying padded envelopes in bulk and printing postage stickers on the Pitney Bowes machine. (inc.com)
Don't forget shipping supplies such as padded envelopes, boxes, bubble wrap and tape. (entrepreneur.com)