I have a mini backhoe from Northern Tool. The one they sell today is more rugged than the one I have. It is not the fastest backhoe, but I've dug 120' of a 20" trench 4'-5' deep in clay and hardpan.
It is a good backhoe - had mine over 20 years. I dig drainage ditches, put in sauna columns, culverts, etc. You can always sell it if you don't want to keep it. But the first one I used, I rented. You may be able to find one to rent.
NorthStar Trencherman Backhoe 270cc Honda GX Engine | Backhoes | Northern Tool + Equipment
That's closer to what I was looking for. I should see if I can find anything used for sale, then I could sell it when I'm done.