Tractor Supply sells them around here as well as Big R stores, also Northern Tools online. If your welding/fabrication skills are good, you can build one yourself. I've built several over the years. As far as the plan for fuel, I personally think you are better off continuing to add to your fuel stockpiles instead of the oil thing. A lot of these Mini tractors (and most all newer ones) have pretty sensitive fuel systems/filters. I would also suggest that you install an oversize muffler, or at least have one(and try it beforehand) to help keep the noise down some. I have a large muffler for my welder that while looks dorky, quiets it down A LOT. JMT's
I have a 12 HP Sears tractor also from Our old Neighbour of 98 years old of yesterday. His Late wife bought it with every option that was on the tractor page flyer . I have that flyer & all the manuals with the equipment .. We call the Tractor "Franky" & franky lives with a 3 Kubotas and many other types of machinery . Sloth
Think of the load you asking that tractor,and the load that tractor is designed for. Ploughing is very hard work. Practice with what you've got now and see just how well it stands up to the demand you expect of it . Plan on parts and repairs in the future carb kits, starters pinion gears bearings tires and tubes and so on/ for the plough plan on replacing joints and areas that flex and blades that dig , I recommend hard facing rod . I have a 9N ford that needs some love but usually starts and runs fine but uses a lot of oil . it's old like me. Having a loading bucket is the most important thing because lifting stuff is an every day thing and if you don't have lift equipment and hope to survive, forget farming. Every thing I can I have at least a small crane for lifting ." Harbor freight helps' .
I'm already post SHTF, and am figuring that there will be no fuel to run those powered garden tools when it hits everybody else. My list of garden tools in order of importance. 1. mattock 2. posthole diggers 3. hoe 4. shovel 5. hard tooth rake 6. sling blade for mowing 7. others, but none I couldn't live without. Stout leather gloves for using all the above. No fuel and not enough mules to go around. In the 1860's Midwest a farmer was supposed to be able to till 40 acres and work it all year with only a thick toothed pitchfork. I sold off all my exercise equipment 3 years ago - don't need it anymore, and sleep like a baby at night.