I've used
Arrow:
https://www.arrow.com/
Aspen:
https://www.aspen-electronics.com/
Rutronik:
http://www.rutronik.com/
and RF-Shop
https://www.rfshop.co.uk/
for stuff in the past. Many of these are not cheap but they've got proper traceability of parts, which is important if you're providing any kind of warranty on your work.