Is there a device that can allow you to connect multiple microphones into a single input for recording?

I’m assuming this is for electrical instruments?

In my experience (playing in two bands with recording stuff)..

You either had enough inputs on your mixer/PA… or you didn’t. I don’t know of any kind of “power strip” for inputs like that.

You certainly can find Octopus Cables at most music stores.
It really would be best to get a mixer. You can get low end ones from $30 on up. But you get what you pay for.
You can try Radio Shack to Guitar Center

You can’t simply connect them in parallel. You need a mixer / preamp, which has multiple high-impedance inputs and a low-impedance output. Unfortunately I’m not familiar with specific products.

As @gasman said, you need a mixer board like those used by radio stations and recording studios.

As gasman and HungryGuy pointed out, you can’t simply merge the signals together with a cable, because that will cause a change in the impedance of the signal, and overload the inputs on your recorder. A second mixer needs to be used to correctly sum the signals without an impedance change. This is called submixing. Then your output from that mixer can be routed into your recorder. A submixer should also allow you to route your 6 signals to the output of the mixer via the pan pots on each of the 6 input channels. That way you can “hard pan” signals if you want further control of the two signals once they’re in your recorder (recording as two mono signals rather than as a stereo signal into the two-channel recorder).

You need a mixer, simple as that, they go from the large to the small