Skystar02
For aviation parts try looking at:
ILSmart: Aircraft Parts, Helicopter & Defense Parts, Marine Spares
You will need to apply for a password but you can try it out first. Most airlines
use this site to obtain spares and it also lists the agencies who are certified to
repair a particular part.
If a company lists the part they will also show if it is new, repaired, overhauled,
or 'as removed'. You can ask for quotes and in response they will indicate the
type of certification which will accompany the part.
Sometimes, instead of buying outright you might find it cheaper to ask for a
part exchange. Sometimes the supplying company will agree to this.
Hope this helps.