Janswede,
Engines & Things in Canada make excellent resin engines for the models that you're building. They seem to make a model for just about any aircraft engine that's ever been produced, including jets. Their website is:
www.telusplanet.net/public/engthg
I've bought a few engine kits from them, and have been pleased with what they make. Their prices are very reasonable (usually $7 - $10 for most engines), and they have a reasonably quick turn-around time.
If the URL doesn't work, their address is:
Engines & Things
Post Office Box 48013
St. Albert, Alberta, Canada T8N 5V9
780-458-6782
780-459-9069 FAX
Hope that this helps you out!!