Worth mentioning perhaps the smallest but still usable printer
http://www.pentaxtech.com/
I have actually seen the output from the 300dpi version; stunning and easily good enough for any flight planning material incl approach plates.
Then there is the Canon IP90 which is A4 but is light and fairly compact.
I haven't seen any Sony A5 printers which were actually small, appropriate to the paper size. The common dye sub models are bulky. Most are quite bulky. Maybe they have something new. A really compact A5 inkjet would be handy for printing approach plates.