+3h if to make it so it can change price too.

+Quite a lot more time to make it category-specific.

Or, make it entry-specific, perhaps build using the fields system (distinguishing for a user-filled field).

Thank you for adding the information here, Chris. I realize that you understand the request, and I also understand that it takes a considerable amount of time to develop the code. I doubt the club can afford it, since they're a non-profit organization, but I will ask them about buying support credits

Note: some discussion on here http://compo.sr/forum/topicview/misc/deploying/adding-product-fields.htm?post_id=102663

A thought is to make it so that extra catalogue fields are used for user-entered fields. Those fields would be set as non-visible and tagged (using field options) as field inputs for particular entry(ies). Then the fields API would be embedded on the product pages, and the chosen options copied as notes when you add an item.

It's not ideal, as it involves a bit of messing with lots of fields on one shared main catalogue to serve different entries, but it serves our use case of "being able to sell custom T-shirts and mugs" well enough.