What do I need when sourcing new headlight unit

[Admprb]

Hi there, apologies if this has been asked a million times; I have a 2017 Audi a3 black edition (saloon if that matters) and both DRLs have faded, and have read that if the bottom part has gone, it’s more likely I’ll have to replace the headlight units - but unsure what type of headlight units I’m meant to be looking for… 

also if it’s a risk sourcing them from aliexpress?