I have several bags where I can switch the straps out or add a strap to loops or d-rings. You can do it to any bag that has somewhere to attach a strap.
- add something fresh and new to an old bag
- turn a hand-held bag into a shoulder bag
- turn a shoulder bag into a crossbody bag
- add a contrasting or coordinating colour to an outfit
- are generally broader and softer than the narrow straps that come with most bags
I have two cheap ones from a local chain store (1 x brown/black, 1 x black/white), that can be shortened or lengthened
I have one with more dramatic details on it. The brand is Gabrielle P. You cannot adjust the length on this one but they are available in several lengths and hardware colours.
And I have an Anya Hindmarch one that I found in a consignment store. This is my favourite one as the leather is really soft and comfortable, and the sticker designs are really cute. Instead of lengthening and shortening it by means of loops, it uses poppers. There are three different lengths.