You're right on...you "should" be able to replace the blade with a mulching
one. I know they exist, but not sure if you can get one for smaller push
mowers (I.E. 19" - 20") Just look for one that is the same diameter as the
one you have, and then make sure it says mulching on it.

Great! My mower is one of those self-propelling model. I believe it
must be a standard size mower.

Thanks.

Jay Chan