Make your own ...
perl -E 'for($i=0;$i<1000000;$i++){say "Line $i,field2,field3,",int rand 100}' > BigBoy.csv
Output
Line 0,field2,field3,58
Line 1,field2,field3,4
Line 2,field2,field3,12
Line 3,field2,field3,39
Line 4,field2,field3,41
Line 5,field2,field3,18
Line 6,field2,field3,64
Line 7,field2,field3,13
Line 8,field2,field3,52
Line 9,field2,field3,54
Line 10,field2,field3,24
...
...
Line 999995,field2,field3,8
Line 999996,field2,field3,66
Line 999997,field2,field3,29
Line 999998,field2,field3,67
Line 999999,field2,field3,62