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OK, I tried to do the math here. Something remotely resembling maths, at least.

Assumptions:

It is possible to reach an orbital/horizontal speed of $v_O = 5\textrm{ ms}^{-1}$, for example by running.

The density of the object to orbit is similar to Earth's density, i.e. $\rho = 5500\textrm{ kgm}^{-3}$.

We want to orbit at a height of $2\textrm{ m}$ above the ground. You can get there with a ladder (Yes, you will have to start running on that ladder or something like that....how about stilts?).

No atmosphere or other source of friction.

Layout:

The basic idea is to link the orbital velocity $v_O$ to the radius $r$ of the object. The mass is given by $ M = \frac{4}{3} \pi r^3 \rho$ (God I hope I remembered this formula correctly).

Calculation:

We have

\begin{eqnarray} & v_O & = \sqrt{\frac{G M}{r+2\textrm{ m}}} = 5\textrm{ ms}^{-1} \\ \Rightarrow & M & = \frac{25\frac{\textrm{m}^2}{\textrm{s}^2} \left( r + 2\textrm{ m} \right)}{G} \\ \Rightarrow & 25 \frac{\textrm{m}^2}{\textrm{s}^2} r + 50 \frac{\textrm{m}^3}{\textrm{s}^2} & = \frac{4}{3} \pi G r^3 5500 \frac{\textrm{kg}}{\textrm{m}^3} \end{eqnarray}

which then should give us $r$. I used Mathematica for this because it is half past eleven in the evening and I don’t want to guess solutions to get a starting point for polynomial division, getting:

In: Solve[-4/3 * Pi * 6.67384*10^(-11) * x^3 * 5500 + 25 x + 50 == 0, x] Out: {{x -> -4031.33327417391}, {x -> -2.00000049201392}, {x -> 4033.33327466592}}

That is, if you found an asteroid of $r \approx 4\textrm{ km}$, your dream might come true. However, if it is mostly ice (rather than molten iron, which I imagine would be a pretty good reason to stay in orbit), you will have to correct the 5500 up there to the density of ice, say, 930 , and would then need an asteroid of $r \approx 9.8\textrm{ km}$.

Note that the assumption that $m_{\textrm{Human}} \ll m_{\textrm{Object}}$, encoded in the expression for orbital velocity, is fulfilled relatively well in these cases (five orders of magnitude).

Nevertheless, feel free to point out mistakes :)