For passives, I have a bunch of resistor/capacitor/inductor/etc kits for through hole and SMD. You can buy them on Amazon so they're usually available fast. You don't have too worry much about the specs but definitely learn the basics like electrolytic vs solid state, voltage/current/power ratings, etc.

For ICs search Google for "<part description> breakout" which will often show you Sparkfun, Adafruit, or some other hacker focused shop/blog. For example, some results roughly ranked by obscurity: 8-bit shift register [1], thermocouple [2], air quality [3], CPLD [4], crosspoint switch [5].

For anything more complex than that - for example, a DLP micromirror device - you'll have to dig deeper and search for "<part description> dev kit". Manufacturers usually make dev kits using their flagship chips from which you can easily navigate related parts. Be prepared to spit your morning coffee out at some of the prices of this path though (i.e. aforementioned DLP dev kits are $1k+, easily twice what you'd pay for a DLP projector using the same chip)

I assume that's what your Amazon/Aliexpress searches have done by proxy (I often do use Amazon too for more basic stuff like relays, ESP8/32 etc. when I'm impatient)

[1] https://www.sparkfun.com/products/10680

[2] https://www.adafruit.com/product/269

[3] https://www.adafruit.com/product/3566

[4] http://dangerousprototypes.com/docs/XC9500XL_CPLD_breakout_b...

[5] https://hackaday.io/project/167228-adg2128-breakout