Jacto.
The 3 Gallon unit is good to go. Last count we had three of 'em, and havn't had to replace anything yet, not even a seal.
The 5 Gal unit works great, but wasn't designed for humans to wear...The ergos suck!
Solo is the easy way out. Get 'em anywhere, lotsa parts available and not too expensive. We quit using them because of the things breaking down at the wrong time, and Jacto BP sprayers holding up much better, but you'll get good life out of a solo if you keep 'em cleaned out between uses.
Stay safe!
Dingeryote