you would have to do your own research. Usually there are certain areas in a town where a bunch of art galleries is located, or think if there is a mall which has this kind of stores. Maybe consider asking the stores you buy your supplies from if that is not online, that probably would be the easiest.

Anyway, you have to check out different stores or galleries and see whether they carry items reasonably similar to yours. A gallery which specializes in southwest art or japanese art is obviously not going to be interested in your items. After you figured out some possible places you can either check out whether they have artist submission instructions on the web (a number of galleries do) or ask in the store whether they accept items on commission and whom you should contact about this. It is a lot of work, and I would recommend reading through some of the articles in the link below to give you ideas what kind of approaches are more likely to work. Keep in mind that a lot of stores keep about 50% commission.