This is what I have come up with after much research and advice here on TBN.  I debated about several styles, 3 point vs. trailer vs. skid type.  For my needs, hopefully this will work.  I wanted it easy to transport, able to fill with water at home rather than on site, quick, and not dependent on having a tractor, and of course, cheap!
I bought a 275 gal. tote, and plumbed it with common hardware store items.  The pump is the mac-daddy 12 V. pushing over 6 gallons per minute.  It was the most costly thing, about $250.  The jet is a tee jet boomless found at Tractor supply.  It has 5 nozzles, but I had to plug the outer two as it just sprayed too wide for my usage.  Even with them plugged, it sprays about a 
35' path.  I need to play with the PSI  and angulation and height of the jet.  I connected it to a deep cycle battery, but will eventually wire it to my upfitter switch on my dash, and have a plug in.  THe hoses have quick connects and it also has a spray wand for occasional use.  I will try it out soon to spray my plots and road ways with Roundup.