Aprils birthstone is the diamond, personally I think that is unfair as a diamond is pretty much always a great idea for a birthday present, but maybe that's just me. So if you are planning on buying someone a Charm for an April birthday then look no further than any of the beautiful diamond charms available from Pandora.
Gold and diamonds not quite in your price range? Then you can get some equally nice silver with gold highlights and teeny tiny diamond charms from Pandora too.
Or if diamonds are not your thing you can get a lovely range of cubic zirconia beads and quartz beads, and if you don't tell anyone they aren't real diamonds I sure won't. Pandora's official birthstone bead has a lovely quartz bead as a dangle, which I think would be a nice touch on any bracelet no matter when you were born.
Or from Chamilia you can get a lovely sterling silver and quartz heart or crystal spacer bead bead that anyone born in April would be happy to receive. That is a terrible picture of the heart bead, but the best I could find, it does look much prettier in real life.
For those of you like me that like to mix and match your charms even Thomas Sabo has a birthstone charm.