If you had any links/diemnsions this would be highly appreciated 
Derailleur hanger: M5x10mm, socket head (
https://de.aliexpress.com/item/1005004204602992.html)
Seatpost wedge: M6x30, low socket head (
https://de.aliexpress.com/item/1005006778879410.html, funnily this set for the headset, is the only option found a ti screw with low socket head from Ali)
For the bottle cage screw: Take some M5x12mm with 3mm hex key, beware that you need 5 of those.
For the saddle clamp I can't help as the stainless steel ones supplied are doing a good job and also the handlebar screw are doing well so no need to change them in my eyes