I also have a 9' pontoon for fishing. Pontoons are fairly low volume and only need about 1-3 PSI air pressure. It takes only a few minutes to inflate them by hand, even with a cheap pump.
I use a cheap plastic double action barrel pump like this one...
Standard Double Action Inflation Air Pumps
I think I got mine for around $3 at a thrift store, it has lasted for over 4 years.
I looked at the K Pumps but was turned off by the price. All pumps are prone to getting damaged by sand and dirt and all of them get get knocked overboard and lost forever. I also found the cheap pump was much easier to disassemble for a field repair or cleaning.
With the money I saved I got one of these...
Kwik Tek AIRHEAD® 12V Air Pump
If you are concerned about saving space you might consider this...
When closed up they take up just a little more space than a big sandwich.
River and beach envioroments are really tough on gear. One of my friends gave me some sage advice 'Never take anything on your boat you are not willing to loose' I would much rather drop a $5 pump over board than an $80 K Pump.