There are a number of things that influence your ranking. You can pay to promote as the top 2 are usually promoted listings in the list. If you have enough regular sales and more than your competition that will get you near the top. As you only sell one product type that will help with your sales history for that product.

I had a listing that would rank number 1 above promoted listings with over 70 sales but when I ran out of stock by the time I got more I was back down the list and has taken 6 months to get back up the list to be in top 5.

Remember top search results are highly sort after so everyone is trying to get there.