Grass shears

Please can someone recommend a good SHARP pair of shears for the edges of my grass plot?  (I don't kid myself it's a lawn.)  The two pairs I've bought so far are as much use as an ashtray on a motorbike.

First I bought a pair designed for one-handed use, with a swivel joint so you can have the blades flat or vertical.  They are OK if you don't want to cut more than three blades of grass at a time.  And if you don't mind them falling to bits because the two small screws that hold it all together keep working loose and falling out.

Then I bought a long-handled pair, also not sharp enough, and I found the angle of the blades made them awkward to use.   Standing to cut the grass and then stooping to pick it up is more bother than doing it all on my knees.

I wonder if I'd be better off with a sickle?  I don't mind how much I spend (within reason) because I've learned the hard way that cheap garden tools are usually a waste of money.