I'm guilty of the occasional are->'s contraction when speaking quickly, but I'd never just substitute are->is because that doesn't save a syllable.
there are a lot
Also, your example is ambiguous because "lot" is a singular noun (you wouldn't use "are" if the object is a parking lot, for example) but if you're truncating a longer phrase like "a lot of widgets" then "a lot" is modifying a plural noun (you'd definitely use "are" for that, or the informal apostrophe+s we're discussing).