I grew up in the clothing biz and there are successful reps who already go to those shops; warring, you will be new and untried in terms of repeat biz; reps respond to he who yelled loudest LAST.
It's the easiest way to get started. Check references, ask why they would be willing to add another line, how are they going to market / sell the products
They have to have a reason to want it vs just one more thnig to sell...
also, it might not be fun, but on the 1st go around i suggest you travel with them so you hear first had what the retailers are saying and what they want... then get the reps opinion to see f the reasons the retailers gave was the real case or not.
best of luck,