Most servers sell them for 8g each...just earn some money. Maybe you can make alts on the same server, and make doubel, triple, oreven quadruple money while afk-ing.
You can also farm mobs on Pet Island to get rare spawning morphed pets. Sometimes it takes a LONG time, or sometimes a substantial amount of time, say 10 minutes or so.
Other than that, just buy with crystals, or hopefully have a fgood friend trade them to you for something equal in value.
on Kaymo mountain people claim they are worth 30g -.-
This depends entirely by what server you play on. Each server has it's own market value and in some servers the morph crystals might be really common while on others it's rare. Ask around and you should see a estimate of the value. like if people say between 10-30g you can guess that best value to ask/offer is somewhere in the middle