Hi susie. link below will take you some left handed trowels but haven't seen 'smaller' versions before. Not being funny (as my wife is always telling me) but surely the weight of the trowel is determined by the amount of addy you lump onto it? http://www.buybrandtools.com/acatalog/notched-trowels-rubi-flex.html
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trust Dave to beat me to it!
Bear in mind that thick rubber grips are more ergonomical than thin grips (better for your elbows and hands), if that's what you mean by "small" trowels.
Thanks for all the replies. Having seen a friend with a small plasterers trowel I was hoping I could get a notched trowel in the same size - just for small awkward places.