Manual cement mixer

Hello, I am trying to find a genuine manual cement mixer. I have an electric mixer capable of 250 lbs of premix, but would like to possibly convert it using a large diameter turning wheel (with handle) to replace the electric motor. I'm sure arm strength is plenty to turn a cement mix, no pedal contraption required. Aside from references to 100 year old mixers, the only modern version I have found on the web is one made in Africa for villagers, but is produced for export. For you entrepreneurs out there, theres an idea - sell an electric mixer with an easy manual conversion. I don't want to hear about gas powered mixers (too expensive, too heavy too much maintenance), or mortar hoes (have one), or the Mortrex tool (have two), or tarps, etc. I have mixed many, many yards of concrete in every way imaginable, but a manual mixer on a stand would be ideal for projects that can't be reached by extension cord!
Thanks in advance!

Are you sure your cement mixer is not set up to be a manual one?

I have an old Sears model that has its big pulley drilled for a handle, it just does not have it installed because it would be a liability flying around with an electric motor spinning it, but a handle (or bolt with pipe could easily be substituted) can be inserted and used manually. Mine has a Sears Tag but in looking up images and part numbers for it (I would say it was made in the 1950's) it was cloned and made by one manufacturer who sold it under many name brands.

Either way I use mine all the time, but seldom for mixing cement. I use it more to mix up potting soil or garden soil!!

http://www.acmemixers.com/manual-concrete-mixer.htm

http://www.motherearthnews.com/diy/homemade-cement-mixer-zmaz80sozraw.aspx