Assuming your tank's big enough, any of the twin-tailed fancy goldies that lack the exaggerated eye characteristics of varieties such as celestials or bubble-eyes would work with those you have.
Some options are fantails, lionheads, pearlscales, pom-poms, veiltails or ryukins. You could also probably manage moors - despite their exaggerated eyes - as they aren't as prone to damage.
Just a note - the issue with choosing them is not realy the number of tail fins - it's the body shape. I'm telling you this because there are fish such as nymphs that have a single tail but would still work fine with yours and there's also double-tailed fish such as the wakin that look more along the lines of a common or comet goldie and are best avoided. The reason you need to choose like this is to ensure that all fish can get a share of the food and are not out-competed - you see the fancy goldfsh can't usualy swim as well or as quickly as those with the more common-type torpedo shape.