Yes you can buy hub-rings for the non-hubcentric rims...it helps center the rim while you are torquing down the lugnuts.
Now, there have been many many arguments as to whether hubcentricity is really all that vital. Some argue that the hub does not really "carry" the load and it is the lugnut/bolts' job. So, as long as you torque down the lugnuts properly (say slowly in a star pattern for the 5-lug hubs), you would be okay.