Why not just use a large magnet on an adjustable pole, like the ones you use to pick up nails after roofing.
You can get them at any hardware store for a reasonable price.
When it comes to retrieving bobby pins, I find that scoops just get in the way (lol).
Or you just use the magnet from a hard drive gone bad, tie it to a string attached to your belt
and troll for boby pins while you hunt and create a line to grid off while you hunt. You could also bob for a target which has fallen out of your scoop. If nothing sticks to your magnet, so much the better as it could be a small piece of jewlery. This way, you don't have to clean all those nasty fish hooks, spikes, and other sharpies out of you scoop with your hand (good housekeeping approved).
If you detect with an Excalibur, only use all metal metal mode for boby pins.
This way you will get a tone which is easier to dig on than a null on those desolate or sanded in beaches: " home home on the beach where seldom is heard an encouraging word/tone".