Commercial wineries get a lot of their argon from welding supply houses, so there’s no reason you shouldn’t, too. The only thing that I would wonder is just how much argon you’ll really need. These companies typically won’t sell their gasses in anything much smaller than a large, upright cylinder (usually about four feet high). A home winemaker might be able to use that much argon in a year or two, but I don’t know how much wine you make or how much argon you like to douse your wine with.
For those who are wondering why we’re discussing argon at all, winemakers meter out argon gas on top of their wines in carboys, barrels or even half-consumed bottles in order to keep oxygen away from the wine. Argon is much heavier than air and will therefore displace it when introduced into a container. Oxygen oxidizes and subsequently ruins many of the delicate aromatic qualities inherent in wine; it also provides an environment in which damaging bacteria (like those that create vinegar) can multiply.
Just in case you want to experiment on a less-than-industrial scale: Argon can also be purchased in small wine-bottle sized canisters from winemaking supply shops or catalogs that cater to wine connoisseurs. These small, portable argon dispensers are used to keep oxygen from damaging half-drunk bottles of wine and will amply serve to blanket a few carboys of wine until the wine can be finally protected by being bottled.