do you think it would be possible to make a frog/fish spearhead from a small gardening fork? If not does anyone have any other ideas of how to make one? Or even a website?

Just look through a collection of cultural artifacts from any fishing culture. Multiple pronged spears are easily fabricated from a green staff with one end carefully split and shaped, wedged and tied into the correct pattern and allowed to dry. Or, you could lash carved bone or nails to a shaft. Welcome to the world of expiremental archaeology. Next week- Hiker Don and Chris demonstrate that Europe was discovered by Tlinget Indians in cedar canoes ;O)

thanks, but I ment, how could I make one to put in a kit, because its unlikely that I would be able to find one here in the UK

The commercial frog stickers I've seen are rolled steel sockets with welded 3-5 tine pitchforks. With practice they are effective for fish. Frogs are actually easier caught with a treble hook baited with bright red cloth and dragged toward you until snagging is possible ( information from Chris Janowski of WSI ). I've made fishing spears by simply wrapping 3 long curved, sharpened and barbed lengths of steel to a shaft. Just scribe 3 channels to help orient the barbs and lash with paracord or wire.

(For Junior Tom Brown's...) Frogs are an excellent trainer animal for stalking and catching by hand. You can 'hypnotize' them with one hand or a flashlight and then just pick them right up. The spear may still be useful for fish, but even there, a standard mini-kit of lines/hooks/etc. is smaller and lighter.