Rotating the pair of (tank and vehicle) around a common center, and pumping "up" through the center, could work. But the pair would be very off-center most of the time, and unstable unless attached end to end.
Flexible couplings are hard to keep flexible at -200 C. But the real issue is keeping the fluid pooled around the pump intake, and not distributed in blobs throughout the tank, interspersed with gas.