I picked a double flare kit at my FLAPS for about $20 and have used it a couple of times. Similar to the one that Griggs linked to. I think it's MIC (Made in China), but works respectably well. I used it on some 3/8" steel tranny cooler lines with good results.
They had the same thing as a loaner (deposit the sale price and refunded on return) but I decided to buy instead. You could try the loaner approach and see how you like it at no charge.
