Hi,
Part number for the cable 50.GCCN5.001
Part number for the HD caddy kit 42.GCCN5.001
You can get in touch with Acer service centre in your country to find out the Partner Retailers near you or search on the web to find a store near you.
For example, https://compupartsolutions.com/shop/hdd-caddy/42-gccn5-001-acer-r5-571tg-59-hard-drive-caddy-kit/