[Mudit]

Cross filter reports can only created for those objects that related child objects.
Most probably your 'Product' object don't have any child object and thus the filter is not available.

Now if you are using a custom report, and the filter is not available, then the reason maybe the incorrect configuration.
Now there is an easy hack to check which object are related to your 'Product' object.

Go to setup and in quick find search Schema builder.(Hint: Its in build tab)

Once there search your object, in case 'product', and click on the search icon next to product.

You will see you object box with all its fields. You will also see some lines going in and going out of the box. These lines represent which object is directly related to your product object, and if it have a one-to-one or one-to-many relationship.

So you will only be able to create reports with cross filter feature only for objects that are related to product objects.

Now if you find that there is a relationship and you still not able to see the cross filter report, and this most probably be happening in custom reports, then you may have to tweak you report settings a bit.

You can do that by going to setup->create->report types->(edit report type)

Hope this helps.