Thanks for helping to bring this to our attention. I was able to reproduce the error you described when attempting to use the "Find Product" tool for this category, but I am not sure why this has started to occur so I have passed the details of the issue over to our technical team for further investigation.
I see that you recently filed a support case about this issue and we will follow up with you again through that case as soon as we have been able to find out more about why the Find Product option is not currently working for this category.
Fortunately, eBay does not require that product catalog details be provided when posting in this category so, if you wish to post items in this category immediately, you should be able to list them without catalog information and then add the desired product details through the eBay Revise your Item form once posted.
We apologize for the inconveniences this issue is causing.