have a look at the PIOsolver blog - there is one on this topic

You might want to think on your own and separating flops considering few factors, that's how i did it. Considering how many factors you will take into account will determine with how many flop types you will come out.

For the example ill separate cards into high/mid/low cards,
High being A-J
Mid:T-8
Low:7-2
Example:
Just thinking about number of high/mid/low cards on the flop will give you 10 different flops.
If you take into account ithat every flop type might be rainbow, mono or 2 of a suit that will give 30 flops.
Are any of the cards connected? 60 flops.
Is the flop paired? 114 flops.
You might separate Axx flops into a different category, that will give you 180 flops.

So it really depends on you, into how much detail you want to delve.

Pio link of Flop subset's