The only way is to get a action replay card and use catch trainer's Pokemon when you fight your rival.
Chat with our AI personalities
You can get another starter if you get all the sinnoh pokemon. Proffeser rowan will ofer a johto starter.
Trade it in from another game.
No it is a starter in the johto region.-evolved from a starter
Cyndaquil is a starter pokemon from the Johto region and like all starters, it cannot be found in the wild. You receive it as a gift from Professor Elm and it will become your first pokemon. If you want more than one Cyndaquil or chose a different starter and want a Cyndaquil, you’ll have to trade from another copy of HG/SS. If you chose Cyndaquil as your starter and it’s a female, you can breed it and the Egg it produces will be a Cyndaquil. Other than these three methods, it is not possible to obtain a(nother) Cyndaquil.
In Pokémon HeartGold, you can find the White Flute in Route 47 in the Johto region.