I think a 36 hole, double walled Sunrims CR-18 is about as good as it gets for very little money. You should be able to pick one up for $30.

Of course, having an excellent rim is only half the story.

Are your spokes in good condition? What's the brand name? Good quality spokes can be re-used and give you many,many miles. If so, you might try to match up your spokes with any rim mentioned above.