Stefan those at Lowes are not locking casters you can save 40 cents I guess by not buying the HD ones but I am sure HD actually I know has non-locking also.
The originals almost always become bound up somehow and are impossible to turn. I have tried soaking them in hot soapy water and other stuff, but somehow, the become fused inside never to turn again.
You can buy Weber replacements, but you can also buy them from places like Menards or Home Depot. The Menards and home depot ones won't have the locks on them however, but I dont consider that a big deal. The way I remove them is to get a WIDE screw driver or a dull chisle and place the blade pointing down towards the wheel right where the plastic meets the metal frame. Then pound it off, rotating sides a couple times if necessary. I have pulled many of them off and they usually have rust, but none ever gave me too much problem. The originals almost always become bound up somehow and are impossible to turn. I have tried soaking them in hot soapy water and other stuff, but somehow, the become fused inside never to turn again. I think I pay about $5 or $6 a pair for them in the home improvement stores. You need to save the original plastic part that goes into the grill leg though, the ones in the store just come with the metal rod that goes into the plastic part. They don't come with the entire wheel and plastic insert.