I'm also new to disc detainers (so I'm excited that I finally was able to buy this pick), but to help myself learn, I bought what Amazon calls a "AmazonBasics Keyed Padlock". I figured in addition to being a learning tool, I might find some additional practical use for it at home (because it looks like a decent lock). LPL shows it in this video:
https://www.youtube.com/watch?v=JDNoMbjxBMI
The Amazon listing for it is here:
I think this should be the same as in the pic as well as much cheaper then $50 cad https://www.amazon.com/dp/B07SZ73BFF/ref=cm_sw_r_cp_apa_i_n3laGb689E70J