I've never been into tabletops, but I might convince myself to sit and watch as I produce new bags or bracelets.
If you go in there and make the dicebags while people are gaming around you, you could easily generate more income.
Just be sure that if you are making dice bags for the store, that you don't make the same thing for customers under the table. You probably already recognize that the site would not appreciate that, but I don't know you
Bring in some examples of other cool chainmain thingies, and sell those to people. If you make a few sales of other things, you can then talk to the store owner and see if they want to buy some of those as well - or you can keep it completely separate and just make dicebags for the store, and everything else only by direct sale to you.
The simple respect you will get from most people for making cool stuff will almost guarantee you some sales above and beyond dicebags if gamers actually see you making them, and you can show them a few examples of other things.