Amazon have a few lego mighty micro sets ranging from £4.92 (add-on) to £5.47 (prime)
Spiderman vs Green Goblin £4.92
Batman vs Catwoman £4.92
The Flash vs Captain Cold £5.47
Robin vs Bane £5.47
Hulk vs Ultron £5.47
There are longish waits on some of these...around a month for some but at least ready for Xmas :)
UPDATE: Mine are actually arriving next Monday. So maybe not quite the long delivery as expected.