You can get the steering wheel puller at your local auto parts store for $10 or $15.
**HOWEVER** - you are going about it wrong. Unless you know that someone removed the steering wheel and put it on clocked wrong (doubtful), you should get a proper 4-wheel alignment done instead.
*If* it is still that way after the alignment, the shop should adjust the tie rods (i.e., adjusting both tie rods in the same direction to maintain the correct toe in but change the direction of the wheels relative to the steering wheel) to center the steering wheel as part of the alignment that you paid for (should have been done without you asking, but sometimes you have to push them to finish the job).
I have done this myself on occasion (I'm anal about the steering wheel being perfectly straight), but if you don't know what you're doing, you can mess things up (adjustment of steering parts isn't something to guess at or experiment with unless you know what you're doing).
(If you think you can't afford an alignment, think again - if something is out of whack causing the steering wheel to be off center, it could end up costing you more in tire wear and ultimately an alignment anyway.)