YeAhx
Galvanizer
Not sure how much security courier bags costs but they must not be cheap. If you are using multiples for each parcels the cost adds up quickly. Only do this for expensive items I guess.Better Idea:
Buy security courier bags (non labelled or of Amazon / Flipkart) for appropriate size, put your items inside it. Use non transparent / non brown tape like that with Flipkart or Amazon name or use void tape (leaves marks when pulled out). Paste a "Do not accept if tape is tempered" sticker / page over tapes on both sides, add a QR code for fun to make it more legit. Now put it inside another security bag and paste the label over the opening of bag / bag seal.