I know you asked about lockbacks, but on a farm, it seems like a fixed blade might do you more good. There are a good number of knives in that price range, that would work well. No reason you couldn't stick one in a pocket if you don't like belt carry. Queen knives with D2 steel cut like anything, mountain man is good if you can find one in your range. They make some linerlocks, old style like an electrician's knife, but I don't know if that's a strong enough lock for you. Umm ther is a traditional type of knife at your price point at one of the approved bladeforums dealers. I'll leave a VM with the name since it does have a pocket clip. All other respects it's fine, stag textured delrin handles, good sized blade, lockback, and decent steel.
Thanks, Neal