Fix for Small Leak from Power Steering Rack?

I would never put in fluid not specifically made for power steering, it can cause more damage. You can buy power steering fluid with an additive to stop leaks but that just causes the seals to swell a bit. I doubt that any fluid would stop a leak like you described. Talk to a local garage or body repair place about getting a used (as in junk yard) one - might be as little as half-price. Of course you have to be careful as you could get a damaged one, which is why you do not want to do it yourself.