OPDs are apparently not required by law in Alberta, for either new tanks
sold or old tanks to be refilled. Some stores stock new non-OPD tanks, but the Costco stores where I have checked lately have
only OPD-equipped tanks, at a good price, which is why I suggested them as a possible source.
I would choose an OPD-equipped tank if buying new, but I realize that I would likely lose the OPD if I used an
exchange service, since the companies which offer exchanges (turn in your empty tank for a full one instead of refilling your tank) in my area have few if any OPD-equipped tanks in their stock.
Again in this area, I would not be concerned about a refilling station requiring the tank to be equipped with an OPD; in fact, the kids working at my nearest station don't even look at the date on the tank. Obviously, practices vary by location. I am prepared for the possibility that if I plan poorly and run out (of both tanks!) on vacation in the U.S., I will likely be forced to buy a new tank.
An in-between
option for old (expired) tanks in addition to those offered by Victor might be to trade the expired tank in on a re-certified (but still used) tank. While the old tank has little (if any) commercial value, the trade-in has sometimes been offered in conjuction with toxic waste "roundups" run by municipalities - I did this a few years ago with our old barbecue tank. This is likely to be available only for the common 20-pound size.