Heck, the venue might not allow glassware sales inside anyway, due to liability concerns.
Let me toss in another vote for
Cafepress. They've really improved the variety and quality of the merch they offer, and the graphics quality has also improved. And best of all, since they manufacture to order, you don't end up with a lot of unsold merch, 100 unclaimed mousepads, 1,000 leftover Christmas ornaments, etc.
As an example of a Cafepress "storefront" and a look at the graphics quality they can offer, here's
the Wraeththu Bazaar, which has artwork and merch based on my friend Storm Constantine's books (as well as other authors and nonfiction she publishes under two imprints).
Now, most of y'all don't know anything about her books or her magickal stuff
, but you can still see the variety of items available (from mousepads to mugs to glassware to magnets) and also see the vivid quality of Cafepress's image imprinting.
--And they even make black t-shirts, finally.
(Although getting t-shirts printed all at once is probably cheaper.)