bubble bags are mad overpriced. if you feel the need to buy them i have a site somewhere you can get the 4 bag set for 90 euros. i use a lesser known brand and get happy results.
i'm almost positive you can't get smaller than 25
cave - it's really a lot easier and better than iso. you need to get purified butane, or you can use ventti, it's anywhere from 3-6 bucks a can. use a liptons ice tea bottle, the larger ones i've found them to be best.
take your plant matter and chop it up a bit, smaller is better. then almost fill your bottle with plant matter.
then make a small hole in the arse end of the bottle.
cover the head of the bottle with cheese cloth and secure it. then point the head of the bottle downwards, into an old dish with a smooth non porous surface.
apply the nozzle to the ventti that you think is best, and insert it into the hole in the bottle. fill the bottle and let it drip into the dish. depending on how much you put in, you will need a few cans.
after a wee while the ventti will evaporate at air temp and you will be left with hash oil. just make sure you wear gardening gloves when you do it, the bottle gets very cold. and dont be silly and smoke a cig or anything when you do it lol