Why and where to buy original and same strap of the watch?

Buying watch is a easy task these days but that the same time we think that the shopkeeper/ Showroom or online vendor is the manufacturer. This old way or thinking is very wrong as these days the scenario has drastically changing. First of all we have to change our mind set and we have to think same way like we think for electronics for example television, mobile, camera or speaker. Seller can be any shopkeeper or online website. But should be authorised and should provide genuine bill for the product we purchase. Same way other electronic industries do have. Watch Industry is