Sorry. I tried but I can not find one either. Kneeling boys usually have their hands in prayer, no hammer there and hammer designs are usually void of a boy.

If you can't find one ask Vicki from here she is basketkase and has her own site and does very good digitized designs for a reasonable price like $1 or $2 per design. Check out her site the quality is excellent.

These may not be exactly what you imagined but may work for you in a pinch.

There is a cute one(not on knees though) in this daddys little helper set on OPW

Also check near the bottom of the page on the link from artistic threadworks there a couple of designs with a boy holding a hammer.

http://www.embhome.com/mall/sunbonnet-p-56555.html
on this boy you could delete the water can and add a hammer.

Thank you so much everyone. I think I can make the one from Oregonpatchwork work for me.