Discovering GET variables

Might not be the perfect place for this question, but do not see a better place on here to ask this. Does anyone have any suggestions for how I can discover a GET method variable for results per page for Overstock.com product pages? I want to be able to pull more than 50 results per page in an http request, but I do not know what the variable would be (like I do know for sort order, index starting point)

I am aware this might not exist, but thought I would ask if anyone has a suggestion for potentially discovering it. I have tried to look for a way to set it with an option on the webpage itself, but do not see one. Thank you in advance for any clever ideas you can come up with!

You can try to find an example in the UI or you can guess, but there isn't a method to discover them.

I mean if they dont have an option on their user interface their php scripts probably arn't using any such variable and if their scripts are looking for one and they dont have it in the user interface then good luck finding it other than trial and error.

Maybe email the webmaster of the site?