Jacto makes a really nice unit. It’ll run you $125-$150, though.

https://www.forestry-suppliers.com/product_pages/products.php?mi=29421&itemnum=13802&redir=Y

The Harbor freight unit actually works pretty well, esp on sale for $19. It doesn’t like diesel, though.

I’ve actually been using the el cheapo $6 specials quite a bit, you just need to spend the money on a good wand and sprayer tip (Conejet 5500 tips are nice, esp the brass ones). When the diesel wears out the pumping device, I just toss the unit, and put my wand on another one.

Wish I could find an electric unit that pressurizes the tank, and doesn’t have a pump that comes into contact with the contents. Diesel/Remedy mix is hell on pumps..