  Using density matrix renormalization group (DMRG) and perturbative continuous
unitary transformations (PCUTs), we study the magnetization process in a
magnetic field for all coupling strengths of a quasi-1D version of the 2D
Shastry-Sutherland lattice, a frustrated spin tube made of two orthogonal dimer
chains. At small inter-dimer coupling, plateaus in the magnetization appear at
1/6, 1/4, 1/3, 3/8, and 1/2. As in 2D, they correspond to a Wigner crystal of
triplons. However, close to the boundary of the product singlet phase, plateaus
of a new type appear at 1/5 and 3/4. They are stabilized by the localization of
{\it bound states} of triplons. Their magnetization profile differs
significantly from that of single triplon plateaus and leads to specific NMR
signatures. We address the possibility to stabilize such plateaus in further
geometries by analyzing small finite clusters using exact diagonalizations and
the PCUTs.
