I own a 10g tank as well and am using this filter:
I chose the Slim S10 for my 10g.
It works just fine and cleaning inside is easy if you buy a cheap ol' toothbrush, so nevermind the reviews complaining about being hard to clean.
Its strong enough to keep the water flowing, but not enough to blow your fish away.
It does disturb the surface just a bit so baffling with a piece of sponge cut to fit across the entire spout and dip into the surface works just fine.
The only downfall is that the intake tube filter sponge is a bit prickly so you'll need to wrap it with a piece of pantyhose to protect your betta's fins.