Redeeming Lotte Gift Vouchers

I received some Lotte gift vouchers as a gift and I know that you can take them to these small shops near the store to cash them in for a 10 % commission. However, I couldn't find any when I went to Seomyeon last weekend. They are normally located in the back streets, but they move location a lot, because they are technically illegal.

Has anyone seen any recently?