Thanks for the comments.
These models are easily available from the major manufacturers of 1:400 scale models. The models shown in the pictures:
AP-BHV - Dragon Wings
AP-BAK - Phoenix Models
AP-BFW - Dragon Wings
AP-BEU - Gemini Jets
The models are priced between $25 and $30 generally, depending on where you're buying them from. www.jetwaymodels.com
is a good source for 1:400 and 1:200 scale models - they stock Dragon Wings, Phoenix and Gemini Jets. You can also try ebay, where you can find good bargains at times.
A good collection of PIA models is also available from Aeroclassics, such as this version of AP-BAK:
The picture doesn't show a lot of detail, but this Aeroclassics model is absolutely stunning - and that gorgeous livery helps!