I bought the Tracey Cox Supersex G-Spot vibrator recently http://www.lovehoney.co.uk/product.cfm?p=24372 and it 'spot on' when it comes to my g-spot. It's on offer at the moment, if you want to give it a go!
You won't notice a massive pleasure zone as soon as you hit it and maybe that's why you're struggling? For me, I don't know if anyone else is the same, but when the spot it being hit, it almost feels like I need to have a wee, which soon passed and changed into something special!
It's not too far in, that's why I don't see the point in people buying massive dildo's/vibrators, just seems like a waste. When my Oh puts his middle finger inside, with his palm facing upwards, and kind of pushes up/curls his finger, it hits the right spot.
Like a lot of women I've worried that I didn't have one. I almost never feel sexual pleasure inside my vagina and so finding my g-spot can be hard. Mine personally needs gentle touches or it is too painful to do anything and it can't be hit by Daddy's cock most of the time anyway. We've stimulated it a few times now with varied results and we seem to be getting somewhere!
If you don't like hard touches, try mimicking the feeling of vibrations or something else against it. I particularly seem to respond to vibration-like finger flicks, which I never thought would work. If you can get a partner to try stimulating it, I think you should.
We recently bought (but have not yet had the time to try) one of these: http://www.lovehoney.co.uk/product.cfm?p=22767 (Lovehoney Satisfy Me Curve Silicone Dildo). It's cheap, body-safe and according to the reviews, does the job well.