First off, if you can afford to buy anything from amazing etsy crafter spinthread you absolutely should. But say that love love this necklace but need a quick and cheap fix.
Grab a thrifted needlework piece (make sure you can bear to part with it) + some double sided interfacing + some pretty fabric for the back side (I used raw silk) + some gold chain. Fuse the needlepoint to the interfacing and then to your backing fabric. Cut out a pretty shape-- it will be nice and stiff and shouldn't fray too much. Go over it with the iron on both sides just to make sure. You can also stitch through it all on (I used my sewing machine) to make it extra secure/ prevent any of the embroidery from coming out. Attach the chain and voila!
You can't tell, but the back is really pretty and bright. * *apologies for the photos-- was in a rush so they're from my phone. Busy doing holiday projects!