For a small mechanical shear that doesn't take up a lot of space, a 12ga Niagara is hard to beat. My dad bought one of those around 1962 for his HVAC sheetmetal shop, and used it continuously until 1990. Sold it to another shop that's sorta across the road from us, and they still use it every day. It partially sheared a woodruff key in the driveshaft once when someone tried to cut 11ga SS with it, and that messed up the clutch/brake timing until we found the problem, but other than that, it has had no breakdowns in over 40 years, and its got to have over a million cycles on it by now.
Since you're in Va, you might call N B Handy in Lynchburg and see if they have, or know of, any power shears for sale in your size range. They deal in all kinds of sheetmetal supplies, and their salesmen usually know what anyone in their area has for sale. They're fine people to deal with.