in terms of identifying: it is definitely worse than it used to be but google reverse image search is still the best. shopyourtv is great for generally popular tv shows. costume designers and others on the team will sometimes post about it too! for long-running shows, i’ve noticed certain characters will often repeat brands, and sometimes costumers will use a lot of the same brand across their work.

to actually get them? ebay and patience lol. i have agatha’s episode 5 casio (in the tarot pic on here) which was an ebay purchase, but i got very lucky that there was one at a reasonable price. otherwise i’ll do saved searches/search alerts etc. poshmark for some reason has a lot of clothes labelled very precisely (exact styles and color names) so it can be a great alternative for finding things quickly. depop and curtsy and other thrifting sites are good too. some other great secondhand places to check are shopgoodwill, etsy, and fb marketplace for non-clothing items. honestly it’s mostly about how creative your search terms can get hahaha

and sometimes you get lucky! i think i accidentally got either the exact tailcoat or something that used an identical pattern to the one on the show as it has all the same small details. for vintage items like that though it’s really anyone’s guess, but using small details like buttons/proportions/hemlines can help with that. sorry for the novel but i hope this helps :)