Is there a way to fill your tires with nitrogen?
I am going to be presumptuous enough to ask what I believe is the question behind the OPs question, then answer that...

The problem is that you have to inflate the tires more often than you like. The question then is what can I do to ensure my tires remain inflated for as long as possible. 

The answers
Tubes - these keep the air molecules in. Thicker is better, as is better material. Dump the super thin light weight race tubes and get the thickest one you can find, I would even suggest giving cheap chain store tubes ago.

Tires - Bigger tires can carry the same weight at lower pressures. Put in bigger tires and run at lower pressure. This has two effects - lower pressure leaks molecules slower, and more volume means those leaked molecules are noticed less. 

Exotics
Look at the no-tubes and 'no puncture' slime solutions - these seal the holes the air molecules are escaping from.

As previously suggested - invest in a decent pump. If you don't have room or desire for a floor pump by the door, get a pump that uses CO canisters (and wear the cost of canisters). If it is still a pain to pump up your tires - discard the plastic valve caps, and get rims/tubes with presta valves - it will take less than 30 seconds to top up two tires. 

You might have guessed all these solutions add weight and move away from the best of the best in terms of performance- well, that is expected, nothing is free and super light weight fast racing tires leak air, after all, as long as they stay inflated for the stage - up to 8 Hours, that's all that is needed and any longer is excess weight.