In my partial mash days, I would mash about 4-6 lbs of grain in my old 5-gallon stock pot/brew kettle. I would preheat my oven to its lowest setting (200F), then mash in in the pot (brew-in-a-bag-style, though I didn't know that was what it was called), then I would put the pot in the oven and turn the oven off. I imagine that method could be easily employed for 2-3 gallon batches. You could drill out a hole for a weldless ball valve, then attach some kind of SS braid and batch sparge rather than brew-in-a-bag. That's what I would do. If you already have a suitable pots (one 4L for mashing and one 6L for boiling and HLT would do it), then the total cost would be as little as two weldless ball valves, some SS braids, and a couple fittings and hose clamps. You could ferment in a 3 gal better bottle pretty easily if you kept it to 2-2.5 gal batches. If you went even smaller, you could do the mash in a toaster oven and ferment in a 1 gal glass jug (the kind that fancy apple juice comes in).