I would recommend against attempting to weld it. The chance of getting something inside that won't flush out right away is very high.

I am replacing my condenser today, and it doesn't even leak. But mine is a parallel-flow condenser and those are very hard to flush. With the time required for a good flushing plus some expensive flushing fluid, plus time to clean the airway, I'm better off with a new one.

Most online parts places don't charge shipping for orders over $50 or $100.