If it is an L6-30P twist-lock (that's what the L is for) than you're probably not going to find a ready-built adapter. It's pretty easy to wire one, just buy a dryer replacement cord that matches the outlet in your house and wire it to a L6-30 cord end, they sell both at nearly every hardware store. You're basically making a short extension cord with the correct style ends for your situation.
One issue you'll have is that a standard 3-prong dryer outlet isn't grounded. The two angled lugs are the two poles of the 240 v, and the L shaped one is the neutral, not an equipment ground. You might be able to come up with an improvised solution by mating the ground from some other nearby outlet (there is probably a grounded 120 v nearby for the washer). I did this once for a welder in a house I was renting, but it's clearly not ideal. On a 6-30 socket, there are two "hot" poles for the power and it doesn't matter which is which, they're both the gold (rarely black) screws. The other screw should be green and line up with the large bent lug, and that's the ground. You could just leave the ground disconnected, theoretically it isn't needed for operation, but it's really not safe.
A 4 prong dryer outlet has a ground, it's the D shaped one opposite the L shaped lug. When you move you can use that safely without any trouble. Just connect the two hot lugs to the black and red wires (rarely both black), then the ground to the green wire. Leave the white wire disconnected and ideally trim it short enough that it won't be able to short to any of the other poles and put a wire nut/tape on it to cap it.
Also since the topic of safety came up, when water and electricity mix you really need a GFI. I know some of their systems come with one, but if you didn't get option then you should have an electrician install one. You can have them install a GFI breaker for the dryer if you really want to keep it cheap, and you could just swap the appliances when you brew. Seeing how much you are sinking in to brewing if you're buying one of those systems, I'd recommend ponying up and having a circuit run to where you want to brew with the correct outlet configuration on the end. You will never regret having it done the right way.