Fried gyoza in Singapore tend to be limited to pork, but there is a place that serves rich tasting tuna fried gyoza, good unagi-don, and tofu.
Head down to Aburi-en, a rather grudge Japanese restaurant, and enjoy very grounded flavors you might find more in Okinawa or Kyoto, than in Tokyo. I like the taste of its unagi, and its Okinawa Tuna fried gyoza, because I am not a fan of anything pork. Some of its seasonal delights include yuzu sorbet and delicious tofu. Go to their restaurant and try them. If you are into tender beef, try their gyudon.