Does anyone know any good sources
Local knowledge. Next time you go on holiday somewhere, visit all the airfields in the vicinity and see what you find, or ask people who live in the specific area you are interested in. I can provide some info for southern Europe if you wish.
And your question leads me to this: How does it work if I want to hire a plane for anything between 5 and 15 hours in Bodø? What is available (SEP/MEP, VFR/IFR)? Indicative prices?