Deans Marine Puffer
Both do Puffers cheaper than Langley BUT you have to do a lot more modelling. The Langley kit falls together and is highly detailed which is why it costs more.
After this, you are looking at foreign kits which aren't a bad option as boats vary so much in size.
Scratchbuilding is an option as plans are available:
You can carve hulls from balsa wood or build up former and plank the outside. Either is a lot of work but worth it for the effect. I'd suggest buying a couple of copies of Model Boats magazine if you fancy this as you'll soon get the idea. I'd also recommend a copy of this: http://philsworkbench.blogspot.co.uk/2012/10/book-review-tiffys-workshop-marine.html as it's a fantastic one-stop guide.
The Deans Puffer is fitted with radio control for sailing on calm water.