Well, for the sake of safety, I will suggest you to buy the solution as soon as possible. As we know that solution is a kind of fluid which is designed specially for contact lenses' cleaning. So if you do not use them to clean your contact lenses, it can be very dangerous to make your eyes infected. But for some cases, you can just mix some pure water with the salt, to make them become salty water. In that way, it can work as solution to be used in cleaning. But you should wash your hands cleanly, so that it can not infect your contact lenses. But you still need buy solution from the glasses stores.
If you have run out of your contacts solution, you can read some sad story to produce tears yourself if you wear the contact lenses. Besides, you can use a few drops of saline solution directly in the eye with the dry contact lenses. Just tilt your head back, and hold the eyes open, and then drops several drops of saline solution into the upper part of your eyes ( you shall avoid the drops directly onto your pupils). Hope this work.
I am sorry to hear that you run out of your solution. Anyway, you need to find some ways to tackle this problem. My advice for you here is to get some water and a small amount of salt, then mix them up and put the contact lenses in the salty water which serves the similar function. And you are good to go. But I still recommend that you get some solution as soon as possible.
Except the solution which is used to soap the contact lenses, you could also use the purified water to take its place to moisture your contact lenses. But the precondition is that the purified water should not contain the impurity. Or else, it will let your eyes get infection and other diseases.
Well, although this is a special situation, but I strongly suggest you to use contact solution. As you know, that kind of solution is designed for your contacts because it contains special liquid and chemicals. However, if you are really in such a special case, then I suggest you to use clean and pure water to be as an alternative. What you can do is to soak your contacts into the pure water for a while and then you can wear them again.
Whatever you do, don't use regular water. It can put bacteria into the lenses which would then transfer to your eye. If you have artificial tears you could use those or a re-wetting drop. Just make sure the eye drops are not the kind that "get the red out". You shouldn't use those for a soaking solution. Or just take a trip down to the nearest place selling saline solution. It's not the most convenient solution, but the safest and most hygienic.