My son's StratoTele had a bridge blowout, and so, he's using my classical guitar as his guitar right now. That's the one I'm willing to let go.
He comes to me last night. He had blown out the D string. In general, I pick up strings in pairs. It really is the only intelligent way. That way, if you break a string, you have spares. Years ago — honestly, I don't know if my seven-year-old was still alive — I picked up a couple sets of Dean Markley ball-end nylon strings. I put the first set on nearly immediately. My son picked up a pair of tie-on strings, which he improvised in installing a while ago. Pretty ugly, sure, but that's how you learn. Well, ugly improvisation and Google searches.
Anyway, I pull out the clippers, untie the strings, start putting the new set on, and realize, hey, there's no D string in this set. I suppose it is possible that I scavenged a spare and forgot about it. Still, it leaves the guitar exactly where we left it.
So, in the short-term, I need to get a set or two of nylon guitar strings, strings that will last. I'll throw in a replacement set or two for my Supro.