http://www.spraysmarter.com/master-gardener-rechargeable-cart-sprayer.html?___store=default#/
I haven't seen this one before but it is priced reasonably , can be towed too, and I have seen a master mechanic spray boom kit.
https://www.sprayersupplies.com/ssbk-7-master-a9466836
Probably would need lower flow nozzles.