I think this can work:
import torch
bx1 = torch.tensor([[1,2],[3,4],[5,6],[7,8]])
bx2 = torch.tensor([[11,22],[33,44]])
temp = torch.repeat_interleave(bx1, 2, dim=0)
temp = temp.reshape(4, 2, -1)
output = torch.cat((temp, bx2.repeat(4, 1, 1)), dim=2)
print(output)

tensor([[[ 1,  2, 11, 22],
         [ 1,  2, 33, 44]],

        [[ 3,  4, 11, 22],
         [ 3,  4, 33, 44]],

        [[ 5,  6, 11, 22],
         [ 5,  6, 33, 44]],

        [[ 7,  8, 11, 22],
         [ 7,  8, 33, 44]]])