Plug Ugly

There's an old bath up at the stables that does for a drinking basin for the horses. It started out as an old, empty and rusted out tub with the plug 'ole missing, but a trip to the ferretería on the beach soon fixed that. For a couple of euros, half an hour's work and a skinned knuckle, plus some cementing and a bit more work, the old bath had became a handy trough. Another trip down to the ferret to get a longer piece of hose (it was either that or move the bath somewhere nearer the tap) and all was well. The bath filled up, didn't leak, and the horses got their drink.
As it happens, one of the nags is a playful brute and one day, it pulled the plug out of the bath and emptied it. This means, apart from the mess, that there is no water until someone comes by and fixes the problem. It turned out to be me and, casting about for the bung, I found a half chewed bit of hard rubber tossed under some straw, chewed and perforated too.
Back to the hardware store. Can I have another plug... this size please. The plug was flattened and hard to measure. Take a 48 and a 54 said the lady, one of them will fit.
As it happened, neither did. One was too big, the other too small. The smaller one is now in our bathroom at home, having taken over from an old and manky bung we've had for thirty years. The new one, with a shiny metal back to it, has rusted already.
So, back to the shop. Look señora, you sold me the unit, so you must have a plug that fits. No comprendo, she answered. When in doubt with angry foreigners.
So, to another shop. This one is the ferretería from Hell. It's a giant and wildly overstocked place where shoppers get lost. You can sometimes hear their pathetic shrieks late at night as you drive quickly past. The quality of the merchandise is highly suspect, boxes with bits missing, old stuff made in countries that no longer exist, wooden hammers that break on the first whack... and I don't like going there without a piece of string and a guide-book.
Their plugs are down in the eighth aisle, turn left, second aisle, right and right again. I eventually discover, a little later that morning, that they don't have anything except 48s and 54s either.
I went back to the first shop. Sell me another unit please, I said, with a spare plug.
We've run out of units, she answered with a certain satisfaction, I think you bought the last one.
So, to the next door town of Turre and its ferretería. 
The story about the horse, tee hee, and could I buy a unit with a spare bung, por favor.
Yes I could.