Those little air canisters -

[VeloVT]

Yes, you will be able to buy a co2 pump separately . That's what you need to ask/look for. Are the cartridges you have threaded or unthreaded? To determine this, look at the neck of the cartridge -- if it's threaded like a screw, you have threaded cartridges; if it's smooth, unthreaded.

You may or may not want to buy your pump based on the cartridges you already have (if you don't, the cartridges won't do you any good unless someone will trade with you). The trade-offs are basically as follows:

1. Threaded Pumps:
Pros:
--MUCH smaller and lighter, and thus take up less room in your seatbag
Cons:
--threaded cartridges are more expensive than unthreaded cartridges
--threaded pumps ONLY accept threaded cartridges
--more minimal design may not be quite as easy to use (pick carefully)

2. Unthreaded Pumps
Pros:
--most pumps that accept unthreaded cartridges also accept threaded ones, which could be useful in some scenario where you run out of cartridges and your riding buddy only has one kind...
--may be slightly easier to use; shield fingers from cold spent cartridges
Cons:
--considerably bigger, take up more room in seatbag

I have both. My favorite is my little Silca threaded pump, I love the simple, elegant, functional design, and it's cheap, easy to use and will last forever:
http://www.biketiresdirect.com/produ...il.asp?p=SNEOL

I also have this unthreaded pump:
http://www.performancebike.com/shop/...tegory_ID=4362
very easy to use, but you can see how much bigger it is.


In any case -- don't buy co2 cartridges at your bike shop! They're way too expensive that way, save that for emergencies and instead, buy in bulk ahead of time at www.biketiresdirect.com or www.bikemania.biz, or some similar site. You'll save 50% or more by doing this.