Used to carry a Topeak Road morph--awesome pump--until I lost it. Not as easy as a floor pump, but best frame pump out there. Carried it in my back pocket.
Now I carry CO2. I get the cartridges at Wal-Mart: $10 for package of 12 vs. $4.50ea at LBS. Never had any problems with them (contrary to FUD you'll hear). I'm sure I could. But I've also had rusted frame pumps or broken seals as well. Everything breaks eventually.
A 12g will fill my 700x23s to about 100psi. Certainly enough to get home. Your 700x25s? Probably only to about 75-80psi I would guess. Since you also do MTB wheels, I'd recommend you only carry 16g cartridges. I do not know if Wal-Mart carries them (I've never seen them on the shelf at mine).